[art_arev]

It is for the non FO unit. I have never used the Metra & not familiar with it. I prefer connecting direct. That is not to discourage you using Metra. The diagram is very simple & easy to follow & colour coded. Make sure the wires from the HU are connected correctly to the harness. Most probably your problem is the trigger from the HU. Look at the Pioneer diagram. You will have a trigger for a antenna & a trigger for an amp. Try both of them separately. Sometimes the voltage for the trigger for the amp is low & not enough to switch the amp on. That is when you can use the antenna trigger to power the amp & vice versa..........

 

[Mike's ML]

When I turn the volume to maximum on the HU, I can barely hear any sound out of the speakers.
Verified the amp and wiring on the truck are okay by re-connecting the original MCS.oldman

If the amp was not turning on you would not get any sound from the speakers. I suspect the new head unit is not supplying voltage to the antenna coax which is needed to power the antenna amplifier in the tailgate of the ML.
Did you try playing a CD which does not require an antenna?
Mike

 

[CGL]

Thanks Mike, CGL,

The connector B has 8 wires and no 1/2 connectors for FO on the back of the MCS. I am trying to avoid going up behind the dash to the amp.

Art,
Thanks for the wiring schematic. Is it for a unit without the FO? I'll try to match them up this evening.

The Metra 70-1786 wiring harness has the four RCA plugs for the speakers, plus 5 for additional (pwr with ignition, pwr w/o ignition, ground, dimmer, and external amp/antenna). There are 3 slots left empty. Do any of these need to be grounded or directed otherwise?

-oldman

oldman,
The amp trigger wire is locate at Pin A5 on the C1 connector (the one with Power and Ground wires), on the vehicle harness. Don't rely 100% on the colors in the diagram. The wire color at this A5 slot may be Orange or Dark Green. Align this C1 connect with your Metra harness and see if the A5 wire aligns with the Blue/White (amp trigger) wire on the Metra harness. It may not align and if that's the case then the problem is solved! (It might be aligned with the dimmer wire!) :eek Might as well double check if all other wires aligns properly!

 

[Oldman2000]

Thanks for the advice Art, Mike, CGL,

Went through the wiring from the new HU as per the diagram/ pin layout.

Speaker wires were checked okay. Each speaker output from the HU was individually connected and presence of barely audible sound was verified. Sound level is the same for the radio and cd player.

Of the 8 pins on the original connector,
A01 - light blue - VSS : Left blank
A02 - Yellow - Diagnostic : Left Blank
A03 - Gray - TeleAid Mute : Left Blank
A04 - Red - Constant on : Connected to constant on functions as expected
A05 - Orange - Amp trigger : Connected to amp/antenna trigger
A06 - White - dimmer trigger : connected and functions as expected
A07 - Pink - Switched Pwr : connected and functions as expected
A08 - Brown - Ground : connected to ground and functions as expected

As you can see A01, A02, and A03 are left with no connections - tried grounding them on at a time - didn't make any difference. Is there something else I need to do with any of these, especially VSS?

There is only one lead out for amp and antenna relay from the new HU (Pioneer FH-X720BT). It was connected to A05. The note in the user manual states that max pwr for the trigger is 300mA, 12V.
Is this sufficient to turn the amp on?
Would feeding a line from Switched pwr (A07) to (A05) fry the amp trigger?

-oldman

 

[art_arev]

DO NOT connect A7 to the Amp!!!! A1,A2,A3 don't have to be connected & don't ground them!. Forget about them.

Could it be you are doing something wrong with the Mitra? Why don't you try connecting direct for diagnostic purposes? You can connect the powers & the ground & the trigger. Then connecting even 1 speaker will be enough to determine if there is a problem with the Mitra connections. If you will have sound then problem lies with Mitra.

PS. Can you post a picture of pioneers diagram?

 

[Oldman2000]

Art, thanks for the info regarding the 12v supply to the amp trigger. Couldn’t get back to the forum sooner due to travels.

When the output was checked for the amp trigger wire it was found to be same for OEM and the replacement pioneer (640mA). So that was not the problem.

Checked the harness wires individually and found them working as well.

After reading Art’s post regarding connecting the wires directly, tried connecting the speaker wires to amp input directly, instead of the RCA posts provided in the back of the pioneer HU (see attached pdf for connections info). And guess what, it worked. I don’t know the technical details well enough to explain why the (HU amplified) speaker output is working through the MB’s amplifier, but not the post designated for connection to the amp. Checked through all the menu options to see if it can be switched through software – without any success.

Just bought some female RCA plugs, soldered them on to the speaker output wires and connected them to the harness. All operating just fine:smile.

I must say, the sound quality through a $120 aftermarket radio, albeit 14 years newer, sounds a lot better than the MB OEM radio/cd changer. Having a blue tooth is a big bonus. I will miss the VSS automatic volume control, as I find myself adjusting the volume more often as the ambient noise level changes.

Also, for anyone considering radio replacement. The Pioneer kit ADTVA133, makes this radio replacement exceptionally easy. Only modification to the vehicle required was the removal of the plastic guides on the inside. A simple hack saw did the job in seconds (a good serrated knife would do in a pinch). The new phone mike is attached to the steering column adjacent to wiper stalk. The small plastic panel to the right of the steering column (where the window fold switch is attached) was gently pulled out. There is sufficient space between the steering wheel and the plastic panel for wire but not the plug. It is an easy access to the radio cavity from there.

Though it was a little difficult to get the speaker output issues sorted out, this is a lot better HU (total cost including the kit, harness, & plugs $175) than replacing with used OEM radio from EBAY for $280.

Thanks again Art, CGL, and Mike

 

[dabobenz]

@old man 2000, are you saying you have used a replacement radio set without by passing the original benz/bose amplifiers, woofer & speakers?

 

[art_arev]

@old man 2000, are you saying you have used a replacement radio set without by passing the original benz/bose amplifiers, woofer & speakers?

If you have non FO bose unit you can do whatever you like, sky is the limit.....

If you have a FO bose unit, then you are stuck to the original MB headunit if you want to keep the bose system.

In your case you are stuck, you have a FO unit.

 

[mac128]

tried connecting the speaker wires to amp input directly, instead of the RCA posts provided in the back of the pioneer HU (see attached pdf for connections info). And guess what, it worked.

This is interesting, as I've seen conflicting information on other posts. One said the speaker wires are actual line level, but Mercedes used cheap speaker wire, so one would think they should work with the line level output unless for some reason as you alluded, it wasn't activated.

I have a Pioneer DEH-245 HU, that's hooked up to my original Bose system, with a small balancing device between the HU output wires and the Bose Amp. I'm getting ready to replace it, and was wondering why it doesn't just use the pre-amp outputs if the Bose amp is line level. Also, I'm not sure the new HU is going to have the same needs as the old HU. I was thinking if I stick to Pioneer maybe the output levels will be the same. I unfortunately don't have manuals for any of it. I'll post pictures of my current setup when I open it up this weekend.

I was actually contemplating putting the original Mercedes HU back in which should work beautifully with the Bose, and tapping into the CD inputs for my iPhone, until I realized I don't have the codes for it to authenticate it.

 

[art_arev]

mac there is nothing conflicting. The speaker outs will work into line in of the bose amp. But you will loose quality & have distorted sound at medium to high volume levels.

You can make a rca cable to connect your pioneer line out to the line in of the bose amp. By connecting line out of the pioneer to the line in of the bose you wont have output level issues.

 

[mac128]

Interesting. My Pinoneer was a professional install, and all of the Bose leads are from the speaker outputs of the HU, not the preamp. Then again, I only have a "Rear" pre-out which means I'd have to split the signal to use with the Bose amp and lose control over the front-rear fader, which is probably why he did it the way he did. Essentially he used a Peripheral Electronics VEN 4.5 line output converter. So this makes some sense if the Bose is line level input and he took the speaker level output, he would need to step it down to match the line level. I'm curious as to how this affects the overall sound quality since a speaker signal has different post-amp characteristics from a clean line level signal.

Nevertheless, it seems like if I replaced with a newer HU with line pre-outs, I could lose this converter altogether then, per your comments. But I'm thinking of switching back to my Mercedes OEM HU, which unfortunately means I have to reconnect the 14 previously snipped wires to the wiring harness. Can I just get a new one from Mercedes with leads to work with?

P.S. Just out of curiosity, it looks like he snipped 13 wires on the Mercedes harness, but there are only 12 wires coming out of the Pioneer ... So he must have combined two of the originals as all are spliced together. Any thoughts as to which two? I didn't really see this until I was looking at the pictures later, of course I can always trace them...

 

[art_arev]

Your Pioneer install inspite of being a "professional" install was a compromise, due to only 1 pair of line outs(rear). A new HU with front & rear line outs will eliminate the compromise if the installer does a proper job. Quality wise, if you have a ear for music you will hear the quality difference.
I don't understand why would you want to go back to MB HU.
Reconnecting the cut cables will be the way to go. I don't think replacing the complete cable is that easily doable........I wouldn't even go there........

 

[mac128]

Hi thanks again for the reply. I didn't mean to replace the entire cable, but rather get a new harness to space onto the cut end, rather than splice back all the tiny wires to reinstall the original MB head unit.

As for why I wanted to go back to the MB HU, I'd say the reason why was because I assumed it was EQ/calibrated for the Bose system -- which is probably not true at all. Plus, I already own it, and thought it would be relatively easy to add an aux input (which it's not since I don't have the CD Changer installed), and I thought I might be able to tap into the unused phone pins if I could figure out how trigger the mute function. As it stands, it's looking more and more like buying a new HU that actually does what I want than trying to hack the MB HU.

 

[art_arev]

Aftermarket units are far more advanced then the MB ones. You can "calibrate" your EQ as much as you like. And the sound will be superior to the MB HU.
But, make up your mind so you know exactly what you are going to buy & do.

 

[dabobenz]

If you have non FO bose unit you can do whatever you like, sky is the limit.....

If you have a FO bose unit, then you are stuck to the original MB headunit if you want to keep the bose system.

In your case you are stuck, you have a FO unit.

thanks art_arev,...looks like i would be replacing this old benz HU, its way too old compared to whats obtainable today i.e blooth integration, phone, usb, sdcard, reverse camera etc. can you advice on a good replacement unit ?

 

[Smokiesman]

Put this in the wifes 02! all the bells and whistles !!

Smokie

 

[art_arev]

thanks art_arev,...looks like i would be replacing this old benz HU, its way too old compared to whats obtainable today i.e blooth integration, phone, usb, sdcard, reverse camera etc. can you advice on a good replacement unit ?

I am posting the links I posted for you in another thread
http://www.benzworld.org/forums/w16...ums/w163-m-class/2202129-just-got-2005-ml350-some-questions-2.html#post10718177

 

[mac128]

The speaker outs will work into line in of the bose amp. But you will loose quality & have distorted sound at medium to high volume levels. You can make a rca cable to connect your pioneer line out to the line in of the bose amp. By connecting line out of the pioneer to the line in of the bose you wont have output level issues.

Just pulled my HU out of storage last week, and noticed something interesting on the label pictured below.

Looking at the label, it seems to be indicating speaker outputs of 4 Ohms, which is a pretty typical speaker output. But if the HU outputs line level signal to the Bose Amp, then at 4 Ohms, it's a pretty non-standard line level output. But what could it mean otherwise?

 

[normanbigfish]

mac there is nothing conflicting. The speaker outs will work into line in of the bose amp. But you will loose quality & have distorted sound at medium to high volume levels.

I second this statement. U loose all the integrity of the Bose system when connecting to speaker out puts. This is what I used for a rca conversion on my 99 w140 with Bose system. Tried speaker out puts first but sounded horrible! Wiyh this harness u can run any aftermarket head unit with front and rear rca outputs. Harness says up to 99 but I believe it should work up to an 01 ML. Correct me if I'm wrong. Here is a pic of harness.....
Julio

 

[art_arev]

Mac, most probably the same HU is being used in non Bose systems as well. Then the HU runs the speakers direct. That's when the 4ohm info is handy.