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W220 Moderator
5,668 Posts
Discussion Starter #21

Progress report .....................

Well, once I got into fitting the Seat Heaters Sub Harness I now know why the fella who carefully removed it all from the Car he was breaking said it was a real PITA !!

The biggest problem is that unlike a W220, you cannot lift the Carpets out on an R170 without total Dash Removal and HVAC Unit, and this wiring has to run behind the HVAC Box.

The Carpet is like most MB's, heavy foam backing and not easy to fold up around the Brake Pedal, a lot easier to fold up on the Passenger (left) side.

Not wanting to remove all that lot, I got there in the end, but not without a "faux pas" which could have turned out far worse than it actually did .....................

I removed the Brake Light Switch, and the Pin from Brake Pedal to Master Cyl, which allowed the pedal to rise up a bit more, and then there was much Carpet Folding, yanking, wrestling, sweating and swearing before it came free...............

There was a slight pop as it did, and then I noticed a small cast aluminium piece on the floor and the Brake Pedal was now another inch or so higher up :eek

Yep, the Brake Pedal had snapped off the piece that holds the Brake Light Switch it is a one piece cast aluminium Brake Pedal Box :frown

OK, I'll bet thats gonna be a right 'B' think I, (* more on this FUBAR later *), as I prop up the carpet and continue to get the wiring through behind the HVAC Box, threading it from passenger (left) side, using a flexible Engine Dipstick.

So up with the Cable Trunking plastic top and thread through the Cable that goes to the Driver (right) Seat, cable tie it to the rest of the looms working away from Seat location, until i get to the Column area where the loom tee's off, and 2 wires go up to the Fuse Box, to fuse 30 (5A) and f34 (30A) which are not there right now.

Whilst running and cable tie-ing this bit in I also include a thick Yellow 20 Amp Cable for the Active Sub, which on a Bose Car uses f14 (20A), also an empty slot as my Car had no Bose.

I soldered a spare Fuse Connector onto the thick Yellow Sub Power lead and then dismantled the Fuse Box, slid out the red plastic terminal locks and fitted the 3 cable end fuse connectors in their correct locations, re-assemble the Fuse Box and pop in some fuses of the correct Amp rating.

Re fit the Trunking lid, continue cable tieing to the main loom until I get to where it runs behind the HVAC Box, where I run the Yellow active Sub Wire rearward along the Right side Tunnel top loom, under the forward H/U Console and Centre Console locations, where it meets up with the Sub Earth and Wake Up Wires, here I tape the 3 into a loom, going to the Rear Bulkhead, the Active Sub will be fixed to the Cabin Rear Bulkhead between the 2 Seats !!

So, get the Carpet back down on the Right Side re install Drivers Seat, refit Throttle Pedal :wink

Now move to the left of the Car, un clip the Centre Switch Panel and route the Switch Plug wiring up along the Left side Tunnel to Loom pop it under the Carpet here and then out nearer the Switches and plug it in :smile

Time to plug in the Active Sub fire up the Engine and test the Right Seat Bum Warmer :devil

Ass well and truly warm by the time I've figured out why the Sub isn't working, lol, what now seems like eons ago, some numpty (me) dropped in the Phono Lead and plugged it into the 2 into 1 Phono Splitter Lead by the Gear Shifter but didn't pop the H/U to plug into the Single Sub Out lead :big laugh:

OK, time is knocking on, so I fiddle with a few settings, as the Heated Seat now is up to temperature and automatically drops to setting 1 where it maintains a nice comfortable temperature ................................. Success :smile

So after Mel coming out of the house, and moaning about the glorious (but extremely loud) Boom Boom sound of the Reggae beat, I though yeah, time to jack it in for the night.

* But * the faux pas ..............

Closer inspection, upside down under Dash reveals that there are 3 captive studs in the Bulkhead to Pedal Box joint, with 3 M8 nuts which I can actually get a socket on, the pin is already out of the M/Cylinder / Servo yoke and the Brake Light switch is already un clipped .......................

A quick EBay search has revealed a good used one complete with pedal for the princely sum of 拢17.99 inc p+p should be here Wednesday / Thursday.

Unless there are any more hidden fasteners that I haven't spotted it should take about 10 minutes to fit it and another 5 minutes to put back the under Dash trim............. Phew ................

Good old MB, if this was a VAG or BMW product it would probably have entailed Dash Removal, Engine Removal etc etc etc :smile

So, on to the left side today to continue the left Heated Seat Loom down under the Carpet etc, and then finally, time permitting work out a nice tidy way to fix the Sub securely and invisibly to that Rear Bulkhead without having to strip all the Boot Trims out again and remove the Fuel Tank !!

pix ...........


W220 Moderator
5,668 Posts
Discussion Starter #22 (Edited)
A quick update,

The only things left to do is physically mount the Sub, and install a dual USB Socket, (Data & Charging), in the Rear half of Centre Console Arm Rest Box, then refit the Console.

The whole system sounds much more "alive" with the Sub, and will run to almost Flat Out now, (28 out of 30 on H/U), without starting to distort, I've tested out various different tracks / bands and got the Graphic set in the correct ball park now :grin

I have ordered a pair of decent 6.5" Speakers to replace the MB ones in the Front Doors, as they are now the weakest link :wink

I made a small metal Bracket, which attaches to two M6 bolts holding the Passenger Dash Airbag (left on my RHD Car), very close to the centre of the Car, up near the plastic Dash Top between Airbag and Heater Box.

It was wedged up here for a week or so with a bit of wood and gives a good signal, especially bearing in mind I live in a very mountainous area, never lost it's signal once, and all speed limit signs changed exactly when they should, Car location arrow is spot on etc etc

The only bit I haven't re installed yet is the Centre Console rear half, because it's got to be out this weekend to mount the Sub, and also I've got a Twin USB (data and charge) socket to install in the Cubby Box under the Armrest. This can be used for transferring files, it will have my Internet 4G Dongle in one Socket and it will have my Mobile Plugged in to Charge in the other when using the Car

Here's a couple of pics from yesterday morning showing my GPS Antenna Bracket.....................


W221 & Audio Moderator
10,864 Posts
"So after Mel coming out of the house, and moaning about the glorious (but extremely loud) Boom Boom sound of the Reggae beat, I though yeah, time to jack it in for the night."

You and Mel might appreciate the unique version of Fleetwood Mac's "Tusk" played in the opening scenes of the pilot (Season 1 Episode 1) for the TV series "The Americans." Not just the song "Tusk" - the 9 minute or so version played during opening scenes hasn't been released anywhere that I know of other than the DVD for the series, or some of the authorized online releases of that episode. You have to listen to the opening for a bit before it will occur to you that the song is "Tusk."

Another great one is the version of "Watchtower" played as the opening theme for the series "The Young Pope." Both are super workouts for you new sub.

Unfortunately all the sites that have "The Americans" S1 E1 are paid. You can listen to a bit of "Watchtower" here -

W220 Moderator
5,668 Posts
Discussion Starter #24
Hi Warren,

Yeah that sounds good, another one that has plenty going on is Pandora's Box by OMD and Pink Floyd's Dark Side Of The Moon just sounds amazing :grin

As I'm having the mother of all grief with a VW Passat Crash Sensor, and have been supplied the wrong part, (not the suppliers or my fault), it seems around 2005 VW changed the ID of them but used the same part number ................... :rolleyes: ................... So I gave up with it, and having been assured the correct one is now being posted to me I did a little more SLK'ing ..............

I've Installed the Double USB Data Socket in the Console, so that is now ready to just fit in and plug the 2 plugs into the back of the H/U once the Sub is mounted

some piccies ............


9,092 Posts
I made a small metal Bracket, which attaches to two M6 bolts holding the Passenger Dash Airbag (left on my RHD Car), very close to the centre of the Car, up near the plastic Dash Top between Airbag and Heater Box.

It was wedged up here for a week or so with a bit of wood and gives a good signal, especially bearing in mind I live in a very mountainous area, never lost it's signal once, and all speed limit signs changed exactly when they should, Car location arrow is spot on etc etc

On my CLKs I installed both the GPS antenna and the Sirius XM (Satellite radio) antenna by wedging them between the instrument cluster housing (hidden) and the plastic binnacle (the bit of trim you'd bash your head on if the steering wheel wasn't there). I used double-sided sticky pads as belt and braces to hold them in place. GPS and Sirius both work a treat as there's no metal in between them and outer space that could shield the signals (unlike my foil-lined baseball cap...)

W220 Moderator
5,668 Posts
Discussion Starter #26 (Edited)
Hi, @IWantedaJag ,

Yes, thanks for the confirmation on this :thumbsup:

I've had a bunch of folks PM me telling me it won't work because of blah blah etc etc, and I've been trying to explain that this isn't the first time I've done this ........................

For a start I've done a fair few miles over the last couple of weeks with the SLK Navi Antenna just wedged up behind there as you say, and secondly. when I first fitted an Android Erisin H/U in my W220 I just stuck it on top of the H/U, and it worked well, and the W220 has a lot more gubbins above it, plus all the Glass in the Car is laminated and IR proof (I forget the correct term for that), but anyways, all the nay sayers said that wouldn't work either and it did.

There is a menu item on the Erisin in my SLK which shows the Satellites it is receiving and the strength in a vertical bar graph format ..................
There is a helluva lot of the little bars in the green, a few in yellow and 1 or 2 red, I'm no Satellite expert, but to me the little graphic display suggests it is just fine ;)

When I get to finish the W220, I will be hooking the original Shark Fin in to the Erisin Navi, I have the correct terminal and crimpers now to put on the end of the MB Coax :wink

However that is not a priority right now, because it is working so well as is with the Chinese Erisin Antenna ;)

Once again, cheers for your input :)

9,092 Posts
I've heard a lot of baloney about satellite signal strength being lost by glass, fabric roof tops, etc. Think for yourself, if the signal makes it through 17,000 miles of space 5 to 10 miles of atmosphere of decreasing thickness, what the heck is a quarter inch of glass and another quarter of an inch of plastic going to do? Metal, yes, that'll ground the signal, but glass and plastic?

W220 Moderator
5,668 Posts
Discussion Starter #28
That's it all finished for now, the Active Sub is now fitted properly, system sounds amazing :grin

It turns out that where I fitted the Sub high up to clear the opening Armrest the studs actually come out in a sealed box section, so no need to remove the Fuel Tank to access the nuts, but what I had to do was to cut out a square hole just big enough to get my hand in with a short ratchet spanner so I could fit the nuts and washers and tighten them.
Then I fabricated a screw down cover panel to go over the access hole and fixed it with 8 Torx Screws, so if the Sub ever needs to come out it is not too difficult a job now to unbolt it :grin

All that's left to do now is fit a Retro looking C Class Coupe Steering Wheel so I can get Steering Wheel Buttons on this Car which will then control Volume, Track / Station Change and Call Answer / Hang up.

That will require sourcing a few more parts, like a suitable Airbag Clockspring with more cores and doing some research into the CAN protocols on this particular car, so it'll happen later down the line.

Just finished putting all the Interior back together now, so we can start using the Car :laugh

Helluva lot of work went into re manufacturing a spare Centre Console to get the much larger Android to fit (larger than the single DIN OE Unit), and look like the Car came from the factory with it.

This entailed doing away with the Ashtray etc and cutting and relocating the C/F switch panel lower down :wink

The twin USB Socket in the Cubby Box is Data Transfer and a Charging point.

Phone now auto Bluetooths upon entering and starting the Car, and with a USB Data SIM Dongle it receives good 4G Internet. SD Card holds up to 32GB of my music on it, also has AM / FM / DAB, DVD Player plus NAVI, TPMS and Reverse Camera and WiFi too :)



W220 Moderator
5,668 Posts
Discussion Starter #29
So, almost there now ................

I ordered a pair of 6.5" Component Speakers to go in the Front Doors, as the OE Speakers in the Doors are stock, and they are now the weakest link and sounding a little tired at very high volumes, will get them in when they arrive, I had the Door Trims off a while ago to swap the interior pull Handle Trims, isn't too bad, and from what I've been told there is no real hassle getting 6.5's to fit the MB Plastic speaker enclosures ;)

OK, almost there now then (sort of), but needing help to work out how to get the C Class Steering Wheel buttons working ????????????????
Will also try and get some research done on the CAN Bus of this Car and the W203 C Class from which the retro look Steering Wheel was bought :)

I also need to find the part number of the small Wiring Harness that goes from Airbag Clockspring to the Steering Wheel Buttons, as my "Complete" Steering Wheel / Airbag arrived without that :(

Due to all the fabrication work required to fit this H/U and my lack of knowledge or info on SLK R170 CAN Bus, I haven't attempted to connect the H/U to the CAN Bus yet ...................
Functions like Illumination, Boot Signal and Reverse Camera trigger are all "hard wired" using the "SWC etc" Harness, and it all works fine.

Buuuuuut, AFAIK so far this Car is very similar electronically to the CLK 3.2 V6 Cabriolet's, so as this H/U is designed to fit Pre Facelift CLK / C Classes, I'm fingers crossed :grin

The way I see it is this, I have 2 options .......................

1) If it looks like it'll work after some more research, then let's hook it up to the SLK CAN bus and see if it will all work, this will probably need me to source and install a CLK / C "Steering Column Module" (if they have such an animal) ?????????????

2) Hard Wire the 3 SWC 1 and 2 Wires that are present in the H/U Harness, but not sure if that will work with whatever switching the Buttons do ????? Downside of this is I'll probably only get 2 of Buttons to work that way, Volume + / - and then a choice of either Track / Station Change or Call Answer / Hang Up , where with CAN Function, if it's anything like W220 I should get all 3 to work .................

So :dunno: right now, perhaps @pinkster or @Deplore (or anyone else who understands CAN and H/U's) may be able to jog my old brain into a better state of understanding here ;)

For example, I'm not sure if R170 has one (Powertrain) CAN or whether it has a Body CAN ????

If it only has the one CAN will it be OK to connect to that and not end up with say transmission shifting when changing the Volume, or a misfire or whatever else ??????????????????
More learning and understanding needed right now :confused:


W220 Moderator
5,668 Posts
Discussion Starter #30 (Edited)

OK so the new Front Door Speakers are now here as is the replacement Brake Pedal Box from my earlier FUBAR , I'll try and install them tomorrow or Sunday, depending upon work load tomorrow.

So what's next with this install, well, a different Steering Wheel from a later R171 which has Buttons and once installed getting the buttons to work with the H/U ....................

Please don't bother replying to the next bit, it is just my notes and ramblings from yesterday, as I was waiting on parts for 3 Cars here, and so I was whiling away the time getting all my thoughts in one place, the post after this explains why the stuff below is actually probably a waste of my time, and is me overthinking what might actually be a relatively simple job with what I learned late on yesterday and this morning ;)

It is now my view that the post after this one will be a much easier and better solution if it all pans out :wink


I first saw that "suitable for R170" Head Unit when I searched for "R170 Android Head Unit", and so I bought this unit, however back then I did feel that R170 listing is an error, reason being it is not a straight forward "bolt in fit" !!
I had to do some serious surgery to that unit to make it fit my Dash Aperture, which entailed carefully stripping down the H/U and cutting off the Metal Mounting Ears behind the Face Plate, and also carefully sanding down a few mm off each side of the Black Faceplate / Screen Surround so it would fit the centre console aperture ..............

So I don't really think they should be listing it as suitable, most DIY would have probably not attempted what I did, I would not have been surprised if I'd wrecked it, but I was prepared to gamble that H/U money to get the result I wanted and thankfully have achieved, I actually chose it because it was the closest size and retro looking, and it can be hard wired if you can't get it to work with CAN :wink

Working Steering Wheel Buttons will just be the Icing on the Cake :grin

So I've got brain fry, I will now put all my findings so far below, so I can use this as a reference, there are so many post it notes stuck on my desk, they will just get lost over time, as the project progresses !! .............

I have discovered ..................

This R170 is a facelift Car, but still only has 2 very basic CAN Buses, the Car shares many parts with W203, but the CAN networks on W203 are nearer to W220, whereas the CAN on R170 Facelift V6 (ME2.8) is seriously very very very (etc) basic to say the least.

I ran my Steering Wheel part numbers yesterday, also stripped the Switches down, Airbag etc for an "exploratory" :grin

As usual I now have more questions than answers :rolleyes:

Also I printed the Wiring Diagrams and labelled them up for ............

R170 Engine CAN Bus

R170 Interior CAN Bus

These 2 CAN's seem to be stand alone and not connected, and both are Green wire and White wire twisted pairs, Green = CAN L & White = CAN H

I also printed the Wiring Diagrams for W203 CAN System, looking at Steering Wheel Controls, and I've got a VIN now for an R171 so I can look at the Steering Wheel Wiring on that too ;)

Part Numbers of what I have ..............

Steering Wheel came complete with Airbag and Buttons .........

Steering Wheel is A 171 460 01 03

My Switches are part numbered separately .........

Left (Menu and /\ & \/) A 171 820 66 10
Right (Vol + / - & Call Ans / Hang Up) A 171 820 67 10

Couldn't see a p/n on the Airbag unit or the "Horn and Switches Module ???" behind the Airbag I think that all comes as one unit with Airbag, and switches come separate (will clarify this later) :wink

I have also ordered a good used Airbag Clockspring (let us use the incorrect term "Squib" from now on 'cos it's quicker to type), for R170 and for R171, because I will need to get extra wire cores through the Steering Wheel then down Column and into Footwell Area above the Pedals, and may need to make a "Hybrid" Squib from the 2 because I doubt the R171 Squib will fit directly on to my column :(

There is also a "Wiring Repair Section" for the lower column of the R171, which will give me the correct Plug to go in Column Side of R171 Squib, and from there I can make my connections for Airbag Ignitor, Horn, and then either hard wired 3 cores direct from Switches to H/U, or to whatever is needed to produce a CAN Signal to H/U (Steering Column Module from R171 hacked and mounted behind dash somewhere) or does the bit in my Steering Wheel that the switches plug into actually produce a suitable CAN Signal that can just get tapped straight into the H/U CAN ????????????????????? .................

I do know that "Horn and Switches Module" has a circuit board inside it with chips etc, but that's where I'm lost :confused:

Is it these Chips that translate a "button push" into a signal that the CAN understands ?? This is way beyond me, always has been and always will be I'm just "Computer Signals Blind", I've tried to learn over the years but I simply cannot grasp it :rolleyes:
This is where I'm needing the most help with this :wink

R170 Squib A 170 460 00 49

R171 Squib A 000 464 06 18

Column Repair Wiring Section A171 540 40 32

The R171 Squib has the correct plug for the Top 3 pin plug .................. The other 2 Plugs are to plug in Paddle Shifters ..............

Hmmmm , lets not confuse this any more right now, but in case I want to add them later on (cool mod) ...............

Paddle Shift Steering Wheel A 171 460 45 03

LOL, I just found a Paddle Shift Wheel on EBay, complete with Paddles 拢85.00 so I've bought it ............. Just in case

So let's look at some of the physical differences here, and how I might overcome them................

Horn function ............

The R170 has no SAM to switch the horn, it is old skool, has contacts in it's steering wheel, so when you press on the Airbag it makes the contact on 2 wires, so to keep the horn working I'll need two cores through the squib and make some sort of switching possible within the moving metal part of the new steering wheels Airbag or use a relay triggered by the 3 micro switches in the R171 Wheel, I don't think this will be rocket science.

Airbag, original steering wheel has one single ignitor (yellow) 2 pin connector , new steering wheel has 2 ignitors, yellow plug and green plug, presumably a belt and braces failsafe, so lets try plugging in just the yellow one and see if that keeps my SRS Module happy, if I get a fault light, I will have to swap the actual "bolt in" ignitor / bag from old Steering Wheel to the new one, that's the Airbag, again I don't see this as rocket science.

So the other (green) Airbag 2 cores can be used to get the 2 Horn wires through the Squib from Steering Wheel side to fixed Column side, happy days

I think phase 1 will be be soon, and entail actually getting to the point where I end up with my Fancy "new" Steering Wheel bolted on the Car and a working Horn and Airbag system, and all the original R170 parts un molested in a box in case it all goes Tango Uniform, so to that end I'll go buy a good R170 Airbag used :laugh

If that /\ /\ /\ works successfully then I can start thinking about getting the H/U Control Buttons working

Because of the next paragraph, I'm wondering if it might be easier to wire the SWC 1 SWC 2 and SWC Common - "three wires" at the H/U direct to the 3 pins on the switch module and see if my head unit will recognise these in the setting switches menu, but I'm not clear on how to Hard Wire these via the White Red and Black 3 cores that are left in the Squib which MB uses to communicate Horn Push, and Shift Paddles, plus Steering Wheel Buttons over ............... Anyone ?????

This would be relatively easy to hook up and test temporarily as I could just wire a 3 core temp lead to the H/U 3 and the Steering Switch Module 3 and see what happens

That then leaves the last 3 Cores, and now we start to get to need "Sheldon" as the rocket science begins.
Looking at both R171 and W203 Diagrams, the steering wheel switches are fed there is one core that transmits DATA, (that sounds good to me, sounds like the switches actually make and send their own data, I might try and buy a used spare to strip completely apart and see "how it works". The other 2 wires are if I've read the Diagrams correctly Ckt 30 and Ckt 31, which should mean Ckt 30 is Battery +ve and Ckt 31 is Earth (-ve) !!

Right, there is a slight problem here, these 3 wires that appear out of the Squib because the W203 is using the same 3 colours as an R171 namely Red, Black and White, but ...............

R171 WD says

Squib Pin 2 goes to Switch module Pin 1 = Black = Data
Squib Pin 1 goes to Switch module Pin 3 = White = +ve
Squib Pin 3 goes to Switch module Pin 2 = Red = -ve

W203 WD contradicts and it's Squib Pin numbers and functions are not listed,

basically all it tells me is

Switch Module Pin 1 = White )
Switch Module Pin 3 = Black )---These contradict above
Switch Module Pin 2 = Red )

So looks like a lot more digging is needed, I may have to find someone who has a Car with same steering wheel as I've got and find out which one does what

Brain fried now, need to give it a rest.

Over and Out from 27th Feb 2019 :grin

OK, forget most of that and see my next post .............

W220 Moderator
5,668 Posts
Discussion Starter #31 (Edited)
OK, I'm back again

Having had a semi sleepless night mulling all of my post above over I have seen a couple of U Tube video's where the "Tubes" are connecting up switches to their Chinese Android H/U's ...............

OK, I haven't found an Identical H/U to mine, but something very clear came out of watching this:-

In my post above, I have basically been wasting my time, and also, as usual, I was very very much over thinking the whole "Steering Wheel Control" project !!

I do not need to go to all the aggro of trying to "hotch potch" different modules from other Cars into my SLK's very basic CAN Buses, it's a helluva a lot of work which at the end of it all could turn out not to work and even if it does, it may end up causing problems with other stuff on the Cars primitive CAN Buses !!

So what to do now .................

Well, first part of the "Project Steering Wheel Swap" is to actually make completely certain that it physically fits onto the Car .............
It looks good on visual inspection, but fat chicks and singing etc etc

Then we have the issue of getting Horn Buttons to work, and also making sure the Airbag Module is happy with the Airbag plugged in, that is the second stage, doesn't look too taxing, so that's looking good

I have enough bit's here from various EBay purchases and cars scrapped to hopefully sort those 2 items out

The third to last picture is of a spare R170 Clockspring, showing it only has 4 Cores, 2 for Airbag and 2 for Horn, I will butcher this, to use the connectors on the Column Side by soldering them to the R171 Clockspring (yet to arrive and be mildly modded) ................
The R171 Clockspring has the extra 3 cores (green arrow in last pic below) that will go to H/U through it and it has the correct plugs for the 'new' Steering Wheel, so when modded it will plug straight into the cars loom without molesting it

I'm going to have a go at these 2 stages very soon

I've had my Switches apart, 2 switch units with 4 switches, they have 6 wires that go into the "Horn Button & Switches Module Part" lets call this HBSWCM from now on (see first few pics), and then this connects to the Clockspring and on into Car via 3 Wires See pics below.

I propose modification of the HBSWCM to hard wire the 3 Horn Buttons (blue arrows) via a relay to control the Horn Circuit. Also after further testing I will be modifying this so I end up with my 6 Left Switch wires ending up at Common - and SWC1 and my 6 Right Switch wires ending up at Common - and SWC2 , using the actual 3 pin connector at the top of HBSWCM (green arrow) so all this will retain the standard switch plugs and standard Clockspring plugs within the Steering Wheel
Any Resistors and additional wiring will all be inside the plastic cover of HBSWCM so that will hopefully be the only wildly non standard MB part, making any future repairs of stuff that might fail, like the switches or the Clockspring just a fairly straight forward replacement

The real jiggery pokery customised part will be HBSWCM .................

We'll have to wait and see pending further research

Like in the Video above my H/U has SWC Common (an Earth) and then SWC 1 and SWC 2 Wires, so that = 3 Cores, which we have on the R171 Squib, in addition to a pair for the 'old skool' Horn Switching, and a Pair for the Airbag Ignitor ................

So that will work out.

So I now need to work on my Switches and see if they are / (or how to make them) resistance based with an Earth Common and outputs of a "resisted" earth going down a single line (SWC 1 for one pair on Left Side of Wheel and SWC 2 for the other side pair on the Right Side)

To that end this morning I have figured out that 4 of the 6, all coloured Black , wires all go to one side of the buttons, see my hand drawn schematic pics for left and right switches below, the other ends of the switches all end up in the 2 remaining wires, one for each function, but I haven't worked out what is what yet hence the '?' s

These last 2 remaining wires goes via what looks on the board to be loads of tiny resistors, I'm going to rig these wires to a multimeter hopefully later today and work out whether or not they are resistive switches or not

Let's hope they are, and then the only question will be whether these resistances are within the range that can be programmed into the H/U for each button.

Another thing, the Button Setting menu that guy in the Video had showed his Head Unit could take a load of different Buttons, presumably provided they all had different resistance, but (see photie below) which is the Button Setting Menu in my Erisin H/U, first glance it appears to only support Track Change /\ & \/ and Volume + & - ...................

I don't suppose anyone has come across this and knows if there is an app I can add to allow more buttons, or some hidden menu to allow more like the H/U in the video ??

Also ..........

I don't suppose anyone knows what resistance range the Chinese Erisin Remote SWC 1 and 2 Channels work on ??

So far what I have seen looks promising, I'll follow up semi soon with some more pictures but here's what we have right now :-


W220 Moderator
5,668 Posts
Discussion Starter #32
OK, let it be said here first

The fat chick has sung on Phases 1 and 2 of the R170 Steering Wheel conversion see pics :grin

First thing, the Airbag connectors are different shape, so first up I jury rigged the Airbag wires into the R170's clockspring Plug, Airbag sat on top of old Steering Wheel, turn Ignition on and on comes the Red Airbag "SRS" Light, start Engine off it goes just as it should, so no need for meddling with Ignitor / Bag assembly the R170 is quite happy simply plugged into the Yellow Ignitor, can leave the second "Green Plug" disconnected, and use those 2 Wire Cores for Horn when I fit the "Hybrid R171 Clockspring" this all works out a treat :grin
Next I whipped off the old Wood Grain Steering Wheel, and test fitted the New W203 / R171 Steering Wheel, fits perfectly, even still using the R170 Clockspring so I can continue to use the Car for now just without the switches fitted (see pic) :smile

Will soon be moving to "Phase 3", which is modify the Switch assemblymabobs to work on a resistance basis.

Pic's show where I'm at right now, that Steering Wheel fits perfectly around the Column Shroud etc etc, and the one I bought with Paddles is exactly the Same shape / size :devil

Also, now the Airbag and Steering Wheel is fitted on the Car, I can also see an alternative on how to sort the Horn Button issue without using those little Microswitches, if the current draw proves too much for them ............

I can modify it very easily so it will work exactly how it does now by adding a couple of springy copper contacts between the 2 metal bits, exactly as it worked on the Old Wheel.

I did measure the Current Draw when joining the 2 wires together, (sounding Horn), it is 0.18 Amps so there is already a Horn Relay on the Car, happy days :grin

I'm not sure if the tiny Microswitches on the new Wheels Circuit Board thingy will stand almost 2/10ths of an Amp, what do you guys think ??

That would be the easiest route to go

Tomorrow I'm going to whip the Brake Pedal Box in and then run 3 cores from the H/U for testing purposes see what responses I get from Volume Buttons jiggery pokery hocus pocus meddling :devil

Also found another Video that gives some useful resistance figures so I can mod the Switches to work on resistance basis :nerd

Can't use that interface, because it relies on the Switch inputs being over CAN Bus, and that is the real headache on this particular Car, just too much grief to go that route ;)

Piccies ..............


W220 Moderator
5,668 Posts
Discussion Starter #33
OK, tried the Switch packs before molesting them, no dice, seems to just recognise all 4 buttons as the same function, which is whatever you have programmed last, so referring back to my partial wiring diagram of the Switch Circuits, I'm going to have to re engineer the little tiny circuit boards so I end up with the same common (SWC -) to one side of each switch, and then use the 4 separate outputs, which we have on my diagram, so each different resistor has to go in the 4 outputs before connecting them all together and then to SWC 1 !!

I know now I have the technology to get enough Cores through to work the shift Paddles and the Steering Wheel Buttons, 5 cores in total, which is exactly what I have :grin

So really the last part is gonna be the hardest, (for me with rubbish eyesight), cos these little switch circuit boards are tiny.

The 3 wire Switch to Erisin loom is .............

Brown = SWC Common -

Red / Yellow = SWC 1

Blue / Yellow = SWC 2

This is final fixed at the H/U, and the correct length, and also has the correct terminals to insert in the Plug that will go into the Back (Column side) of the yet to arrive Clockspring, so I've left the Cables dangling for further testing and lower Dash Panel off ready to hopefully final fit this next weekend.

The R171 Clockspring is a no go, but I had a look at the one on Mels C class and it is a perfect fit and has 9 cores instead of 4, sadly Mel want's to use her Car , so I had to put it back............

I've ordered a fleabay one for the princely sum of 拢12.99 inc post :laugh

The 3 resistors I have here are just wrapped round the terminals, and by touching them to the SWC Common the Vol + / Vol - and Track > are all working flawlessly .

Below is some piccies to decipher.

I'll go in depth with the Paddle Shift later on in this story, but basically I've found out that the circuit board inside the shifter has 2 solder pads un used, and if you earth one it shifts up, earth the other it downshifts, so I only need 2 cores for that, yep, it really is that simple on this Car :devil

The pic with the screwdriver pointing at the 4 Pin Yellow Plug (this is where Clockspring plugs in), shows the current 4 Core Plug, leading to Car Wiring for Airbag and Horn, W203 C Class has a 9 pin version for it's Clockspring which fits this Column perfectly, so I need this plug with a length of wiring attached snipped off a breakers Car then I'm good to go :nerd

Piccies of my skullduggery to decipher ...............


W220 Moderator
5,668 Posts
Discussion Starter #34
OK, got a little more done today, these Switch Circuit boards really are tiny for my clumsy fingers and eyesight, but I've gone for the easy option on the Mk1 set, I have another set spare if needs be .....................

See the pictures, first one is the plug that goes into the switch, easy to dissect and rebuild, I plan on using pin one as my SWC Common (earth) and then 2, 3, 4, and 5 for each switch, and taking the easiest route I will solder the 4 different resistors to 2, 3, 4, and 5 then join the 4 together at the other end and connect to SWC1 I'll heat shrink it all then put a small connector between it and the Clockspring ............

The next pic is disassembled Switch, and then standard Circuit with 4 Micro Resistors and 4 micro "little white thingys" (diodes maybe), so first thing I did was unsolder this lot and bin them.

Now multimeter the board to see what to connect to what

Next up I bridged the connector pads where the 4 (diodes ?) came off, then found I now have 4 times working switches with a 0.002 ohm resistance

There was a ton of Multimetering the circuit boards between each step. Now the nicest way to actually do this would be to get suitable ohm Micro Resistors and solder them across the pads, then one would only need to bridge 2, 3, 4, and 5 internally before the wiring plug and voila only 2 wires one end earthed and the other to SWC1 !!

But I wasn't brave enough this time round, so I just bridged the pads .............

I'll get it all working first with my ham fisted method, there is a bunch of room inside the steering wheel for a matchbox sized enclosure full of resistors and heatshrink

Once the Mk 1 set is done I may well have a bash with micro resistors, (or find someone else to do this for me)

See the tiny components I unsoldered next to the ball point pen in 2nd to last picture, that and bridging the pads with solder was enough of a challenge for me today

Switches are now all reassembled and working a treat, I'm now waiting on my resistors coming before Mk1 step 2

Notice as well that each switch has double contacts, so 8 contact pads = 4 switches


W220 Moderator
5,668 Posts
Discussion Starter #35
No sensible comments then ??

Like .............

"If you weren't such a blind old git you'd be able to solder micro resistors first go with ease" etc etc etc :big laugh:

Get ya all asses over to NW Scotland on holiday and come visit me then !!
It's very boring for me trying to talk to my Customers and Mel / Neighbour about what I'm doing, cos they just stare back blankly as they haven't got a scooby doo what I'm rattling on about :laugh

Yeah, I do have good "Reading Glasses", a big illuminated Magnifier on a stand and a tiny tipped gas solder iron, and I will have a go at it on the spare set of switches when they arrive, but the ones I have now will get it all working, the ordinary resistors I have right now are small enough to partially slide inside the little black plug so will carry on as is for now, see pics below :wink

Basically, the 470 ohm is for Volume + Button (switch plug pin 3), and the 1k ohm is for Call Answer (switch plug pin 2) .............

I'm now waiting on the other 6 different value Resistors to arrive via postie to complete the Left and Right Switch Packs ;)

When the remaining 2 are done for the Right Switch I intend to "pot" the end of the little plug with liquid epoxy so it is all solid with just the 2 wires sticking out of each one, that should make for a nice compact and solid assembly. I'm getting better now with this very small soldering lark, will hopefully progress to micro resistors etc soon :devil

When Mk1 is complete I will then test it all IRL driving conditions, and if it's all good after a while I may have a bash at internally mounting the resistors in the switches :devil

Courier has just arrived with what looks like a Paddle Shift Steering Wheel, and maybe something else for the SLK, I'm hoping I'll have all the bits by the weekend :grin

Enjoy ................


Outstanding Contributor
986 Posts
It's truly fascinating what you're doing Dave!

I do follow very closely, and my steering wheel control units are the same, though the board is different.
If I ever decide to mess about with these, I'll be studying this thread ...

When I got my steering wheel remodelled and re-trimmed, and the controls covers hydrographically printed in carbon fibre, I kept the donor wheel controls, so have a full spare set.

A trip to NW Scotland sounds good too ... perhaps sometime during the [five days of] summer :grin

W220 Moderator
5,668 Posts
Discussion Starter #37
:big laugh: Could write a song titled "The Five Days Of Summer" :grin

Yeah, it was the Steering Wheel with Paddles that arrived, it has a small scuff at about 6.30 position, seller did disclose it, and I knocked him down 拢10, but I'll get it recovered eventually when I get the whole interior done after the V8 install and paintwork, (so that'll be a while yet then) :wink .............

Anyone know of anything I could use meantime, would leather restorer cream or some - such work ??

Resistors were posted today, so should get here before the w/end :grin

Cheers for now ................


Outstanding Contributor
986 Posts
You could try Gliptone? They do touch-up kits with exact match to Mercedes leather codes.

Paddle shifts look cool, and tempting ... I have to remind myself that, as I don't drive manual (never have), these will be just a piece of interior decor in my car :grin

I had my steering wheel done by Jack at Royal Steering Wheels, just over two years ago - (it still looks great) and I'm very pleased with it, although I wish Jack would cover the back of the wheel, and the airbag in real leather too ... Maybe next time :grin

W220 Moderator
5,668 Posts
Discussion Starter #39
LOL, I'm not sure how the Airbag would manage to make it's way through Leather in event of an accident that requires deployment :wink

That said I crashed a 6 year old Car very hard a few years ago, and no deployment, I think the Squibs explosive degrades with age so it is most likely that by the time a Car is out of warranty the AB's won't work anyway ;)

W220 Moderator
5,668 Posts
Discussion Starter #40
Back again after a busy weekend, not all on the SLK either :frown

So, here's the pics of the final extra wiring install, first ones show me installing the original R170 Airbag and horn pairs into the new C Class 10 hole yellow Steering Column to Clockspring plug. Then onto the other 2 sub looms that go to H/U for Switches, and the newly made Paddle Shift pair that will end up connected to the Shifter.

The Yellow Horn Wire is an earth so can also be used for the Common - on the Switches and the Paddles :wink

That leaves 4 cores, SWC 1 and SWC 2 for the Head Unit, in reality I will only need SWC1 I think, but it's connected through there anyways in case I decide to do a future mod like a later model MB Steering Wheel with many more buttons :devil

The other pair are Paddle Upshift and Paddle Downshift, and like the SWC 1 and SWC 2 wires I soldered on the correct connectors and then put them all in the yellow Socket in their correct positions.

All going well you think, and so did I ..............

After verifying that the wiring is all good as far as the Yellow Plug, I refitted all the Dash under panels, then fitted the new Steering Angle Sensor / Clockspring assembly, and the Steering Wheel etc.

Started it up, Airbag light off, Horn Working etc etc, ABS / ESP light on as it requires the turn wheel lock to lock procedure, so I turn it all the way to full right lock, back to full left lock TWANG!!

Clockspring Ribbon Cable broken, now got SRS and ESP lights up :crying

The reason is simple ..............

The idiot breakers who took it off, and me being in a hurry late in the day didn't check that it was centred ..................

When you take one of these off any Car, you should always make sure the Front Wheels are in straight ahead position, then remove Steering Wheel, and as you remove the screws from the Clockspring assy, they stop it from turning, and so hold it in the Centre Position, but of course the retard who removed this one didn't do that and I did the assumption is the Mother of all ...... bit !! DOH !!

So another Clock Spring has been ordered, and I'll be sure to run the screws all the way in and then by hand carefully I'll turn it left all the way and and then back 2 to 2.5 turns to make sure it is centred !!

At least I've only got to take the Steering Wheel off to do it :wink



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