SLK Indicator lights staying on - Possible fix

100733 Views 56 Replies 33 Participants Last post by bjornlura, 4 mo ago

ChrisW-UK

Discussion Starter · Jan 5, 2008

1999 SLK 230 (RHD UK car )

Hi All

I searched this forum to help me fix the indicators which were staying on on.
Got lots of help and was able to eventually sort out a fix which may be useful to other folks.

The fault was in the mulitfunction relay unit - part num 170-820-09-26. (This is a plus £500 unit to replace).
I managed to fix the fault without needing to buy a new one.
One of the relays was sticking due to pitting caused by general wear. A rub with some emery paper got it freed up.

Here is a guide for anyone else facing this. some pics are attached.

The relay is in the big relay box under the bonnet next to the battery. (It looks like it may be a filter unit for the aircon)
Lid on the box has 4 screws holding it on.
The relay unit in question is the one next to the battery (on RHD car)

Now - Remove the plug nearest to the front of the car - you will need to unlock it by sliding the grey toward the front of the car.

There is a metal handle thing at this end of the unit, pull it upwards and it will release the rest of the plugs.

With a bit of wiggling you can now remove the unit from the box.

Unscrew the 5 star screws holding the lid on.
You will see 3 gold coloured relays , the one that flashers the indicators is the one furthest away from the edge of the box. (If you hold the unit with the connnectors at the top, it is the one on the far right.

On mine this relay was sticking when closed.
I used a bit of folded emery paper to clean the contacts which stopped it sticking.

And in true workshop manual speak - reassembly is a reversal of the above.

This may not work for all faults with these units, but it is worth a try.

Cheers

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1 - 20 of 57 Posts

oztds

· #2 · Jan 6, 2008

You did well to get the CCM unit out completely. I tried but was always afraid I would break that big connector.
It's also a good idea to disconnect the battery negative first. These modules don't take kindly to being partly disconnected with power on.

ChrisW-UK

Discussion Starter · #3 · Jan 6, 2008

Thanks for pointing out about disconnecting battery, you can see it disconnected in the pics.
Had too many surprises in the past to take chances.

Cheers

oztds

· #4 · Jan 6, 2008

Sorry, didn't notice the pic - indeed it was disconnected.
Surge arrestor (see other posts) is a good idea too. It stays connected to the second threaded post on the negative battery cable. Don't see one on the pic.

amcfall

· #5 · Jan 7, 2008

Thanks for the info. Mine won't flash every once in a while then starts working again, I will give this a try.

Avery

Nigel Dunkley

· #6 · Jan 18, 2009

Thanks for the pics, I need to try this as mine went last night.

Nig

berk

· #7 · Jan 18, 2009

ya this module is about 700$ from the cheapest place i found so it is worth investigating! Is it possible to replace that relay on the board? anyone have a source for the relay?

PeteB

· #8 · Feb 4, 2009

Thanks very much for this Chris.

I had actually done this and had closed up the module before I found this thread. I had given all the relays a bit of a clean but I was actually looking for a dry joint (none found). After reading your suggestions I opened it up again and gave that relay a good clean-up. So far so good.

One question - how did you know that this relay is the flasher?

tl99999

· #9 · Feb 8, 2009

Hi Chris,

I'm also in the UK and a member of the Merecedes-Benz Club.

I've repaired the CCM/Multifunction module on my 1996 SLK and two others (1998 cars) as well. The permanent fix was to change the defective relay. I managed to source a replacement relay but had to buy a minimum order quantity so I do have some spare relays for sale.

Changing the relay is a two person job as you need an SMD workstation to heat the relay frame (person 1) with the hot air gun while person 2 heats the relay pins on the reverse side of the circuit board with a 80W to 100W wide tipped soldering iron. Person 1 slowly pulls the relay free with a samll pair of pliers. You then you need a vacuum powered desoldering tool to remove the solder from the holes in the circuit board. I have attached some pics of the worn out relay contacts from my CCM module.

For others reading this post I am willing to replace relays in these modules for a reasonable price plus shipping. If it's something that I can help you with then by all means send me a PM.

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YellowSLK230

· #10 · Feb 9, 2009

Nice job tracing the fault down to the specific relay. We have had this fault intermittently for the last few years. I will definitely clean that relay up when I get a "round tuit". Looks like it could use an arc-suppression diode pair across the contacts.

Buellwinkle

· #11 · Feb 9, 2009

I thought about taking it apart but I found a replacement part from a salvage yard for $125 and took the easy way out.

Nigel Dunkley

· #12 · Feb 15, 2009

Gave it a go today, was suprised how easy and fast it came apart.

Cleaned contacts with emery paper and voila !! Very happy

Nig

golfballtx

· #13 · Jun 16, 2009

Fixed it!

I had to get help from my basset hound because that's how mechanically inclined I am! But I now have flashers and turnsignals! The Little Red Sled is back on the road...now if I can find someone in DFW that can strip the flaking interior down to the black, I'd be cooking with gas!!!!
KJ

bisonion

· #14 · Jul 3, 2009

Sticky Turn signal Relay -- Fixed -- Thank you!

My turn signals just failed where they were on but not blinking. I didn't disconnect any of the wiring so I could observe the circuit under operation. I moved the relay armature arm and it began to cycle. So I knew I had the sticky contact problem. I was concerned it was maybe a shorted transistor so I wanted to be sure of the root cause of the problem.

Barry

CYP

· #15 · Feb 18, 2010

hello,

this post should be in sticky. It might help slk users to avoid pay at east 700 - 800 dollars and replace N10/3 CCM module while it sometimes easily can be repaired.

cheers

Ali

[email protected]

· #16 · Apr 2, 2010

Sticky Turn signal Relay -- Fixed -- Thank a lot

@ChrisW-UK: Thanks for this detailed guide which just saved me $700 which was the price Mercedes asked for in order to fix this. You are an angel

Best regards

akontra

· #17 · Sep 18, 2010

thank you

Thank you for your awesome instructions. Have had intermittent problem for some time with indicators stuck on all the time and not flashing. I have followed your instructions and it would appear that the problem is fixed. It appears to have saved me approx $1,000 aussie dollars.

slkjohnuk

· #18 · Feb 7, 2011

tl99999 said:
Hi Chris,

I'm also in the UK and a member of the Merecedes-Benz Club.

I've repaired the CCM/Multifunction module on my 1996 SLK and two others (1998 cars) as well. The permanent fix was to change the defective relay. I managed to source a replacement relay but had to buy a minimum order quantity so I do have some spare relays for sale.

Changing the relay is a two person job as you need an SMD workstation to heat the relay frame (person 1) with the hot air gun while person 2 heats the relay pins on the reverse side of the circuit board with a 80W to 100W wide tipped soldering iron. Person 1 slowly pulls the relay free with a samll pair of pliers. You then you need a vacuum powered desoldering tool to remove the solder from the holes in the circuit board. I have attached some pics of the worn out relay contacts from my CCM module.

For others reading this post I am willing to replace relays in these modules for a reasonable price plus shipping. If it's something that I can help you with then by all means send me a PM.

Hi,

I have the indicator stuck on problem and firstly I must thank you for your excellent posts about the problem. I can't tell you the hours I've spent trying to work out where the offending relay is, needless to say my local MB dealer had no idea, in fact they sold me a plug-in relay that doesn't seem to even exsist on the SLK !

Anyway not having an SMD station, just a lowly soldering iron I wonder if you still offer the "fit-it" service mentioned in the above posting.

Many thanks

Billy22Bob

· #19 · Feb 8, 2011

try mailing tl99999 and asking him.

I'd like to add - the above procedure didnt fully work on my vehicle.
After I did the above, I still found my Right Turn signal still staying on.
I am fairly confident, although I cant explain it - that it had something to do with water in my boot/trunk PSE unit.

2 weeks now since I cleaned and dried it out and I havent had a single issue with any of the turn signals.
The only relationships here are; 1. flasher functions are generated from the PSU & 2. its connected via the CAN bus. There might be some logic code etc with the CCM and its relays
Anyway - if yours are still staying on and the above procedure doesnt work - try cleaning and drying your PSE unit.

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slkjohnuk

· #20 · Feb 8, 2011

Billy22Bob said:
try mailing tl99999 and asking him.

I'd like to add - the above procedure didnt fully work on my vehicle.
After I did the above, I still found my Right Turn signal still staying on.
I am fairly confident, although I cant explain it - that it had something to do with water in my boot/trunk PSE unit.

2 weeks now since I cleaned and dried it out and I havent had a single issue with any of the turn signals.
The only relationships here are; 1. flasher functions are generated from the PSU & 2. its connected via the CAN bus. There might be some logic code etc with the CCM and its relays
Anyway - if yours are still staying on and the above procedure doesnt work - try cleaning and drying your PSE unit.

Thank you Billy22Bob, so far I haven't been brave enough to take the module with flasher relay out of its black box....been a tad cold and wet for doing clever stuff in the drive....will have a go the weekend. Looking at the excellent 'photos that tl99999 posted the case for a burnt relay does seem very convincing, having said that I'm not quite sure I understand the exact failure mode. Is it the pitting casues the points to 'stick' together, in which case this 'stickiness' has to overcome a strong spring, or is it the pitting causes the armature to misalign so it jams against the frame thus preventing it to release. I guess I am just over complicating it.

As you see from a previous posting I have asked tl99999 if he would fit a new relay for me as he doesn't live that far from me (well compared to Aus

Where abouts is the PSU in the boot ? I never never rumaged in there beyond getting the skinny tyre out.

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