R129 - Serious electrical problem… grounded until fixed!

[CWW]

Make sure to also check the condition of the wiring in the ETA unit. It also degrades, and can cause these issues. As long as you're doing the main loom, may as well replace the ETA wires as well. There's a DIY floating around somewhere, or there are shops (at least here in the US) that rebuild them for not too much money.

[Rud]

Today’s findings… Went over all cables, well didn’t strip all cables, but from what I can tell the motor harness is okay. But, I also discovered, with some help from my neighbor, that the stop light didn’t light up when pressing the break pedal. I have cleaned all fuses and checked all groundings, those I could find without a schematic.

One thing I just don’t understand. The break light is so fundamental in its function, how can this be related to anything else then the pedal switch, relay if any, and the wire. And if there is a relay, where is that located..?

I have called the local Mercedes mechanics, and they tell me to bring the car to a car electrician. They can’t tell what is wrong. My own indy is actually a car electrician, but he’s on vacation, so now I’m grounded again, because of the the missing stop light.

But everything hasn’t been wasted. The IR on the driver side door now works 50% of the time. Before it just worked 1 out of 10 times … J

[ctaylor738]

It's common for the wires to break by the right trunk hinge.

[CWW]

I've still got my money on harness issues being the cause of your dash lights, as this is a 1993 with the original engine and ETA wiring. The wiring may look ok, but you don't really know unless you look inside the sheathing. It's the insulation that degrades, not the sheathing. You have to open a bit of it up and see what the insulation looks like.

Pick a bit of wiring, cut open the sheathing, and if it looks like this, then you've found your problem:



In the picture above, you can see how the insulation degrades, allowing the wires to come in contact with each other. This condition regularly causes the exact symptoms your car is experiencing. But hey, if it's working fine for now, then I guess you can always cross your fingers and see what happens. Just be prepared, eventually you will have to deal with that wiring if it's original. It's a known design defect in MB vehicles from 1992/1993 (depending on who you listen to) through 1995, when they finally corrected it.

[Rud]

CWW,

well it’s obvious from the picture, the degration on the wires. And you’re probably right, my harness may look like this too. But how come everything else works okay. The engine spins perfectly, no loss of power or extended use of petrol etc… and everything seems, to related to the electrical part of the break system, ABS and ASR and missing stop light. Of cause it can be additional issues… So for now, I will get the tack/ABS sensors checked, the connectors and cables between these, asap. But as soon my mechanic is back from vacation, I will let him go more into details and get the whole motor-, starter- and throttle harness inspected.

Guess those are the 3 major ones. Excuse me for my ignorance, but is the ETA wires part of one the mentioned or yet another harness…?

Regards,

[Rud]

Hey, if it’s a known and well documented fault from MB, how come no one has ever cut a deal with them, like a harness rebuild or, at least, a heavy discounted price on a new harness, maybe even for free...?

I know the cars from 1992-94 are considered old. But in general terms, how often do you have to exchange harness on other cars only after 15 years, and does this also happens to other Mercedes models from those years..?

Guess I will discus this with the Danish Car Association FDM, and see what they think. I know, no one could foresee this, just 5 years ago; but that goes both ways – the manufacture and the car owner. Now, after 15 years it’s a fact that both parties have to relate to it.

[CWW]

Originally Posted by Rud

CWW,

well it’s obvious from the picture, the degration on the wires. And you’re probably right, my harness may look like this too. But how come everything else works okay. The engine spins perfectly, no loss of power or extended use of petrol etc… and everything seems, to related to the electrical part of the break system, ABS and ASR and missing stop light. Of cause it can be additional issues… So for now, I will get the tack/ABS sensors checked, the connectors and cables between these, asap. But as soon my mechanic is back from vacation, I will let him go more into details and get the whole motor-, starter- and throttle harness inspected.

Guess those are the 3 major ones. Excuse me for my ignorance, but is the ETA wires part of one the mentioned or yet another harness…?

Regards,

Yes, ETA is the Electronic Throttle Actuator.

Also, the other poster was correct, the wires tend to break inside the little rubber tube that runs from the car to the trunklid, that is probably the cause of your dead trunk light.

But the ASR and ABS lights in combination, together with the wiring being all-original, points almost directly to the harness. Definitely get it checked.

[Rud]

Thanx CWW…

Just to be clear on this. You suggest that I, at least, replace the motor harness and the ETA harness.

I have managed to find the part no. for the motor harness: 1295407705 and for the starter harness: 1295400530. But I can’t find the ETA harness part no. Can anybody help..?
Chassis: 1290671F083932
Engine: 119972 12 004279


This model doesn’t have the third stop lamp, so I guess I won’t find the rubber tube to the trunk lid, but have to find the missing power to the stop signs somewhere else. Any idea if this also can be related to the motor and ETA harness issue…?

[Rud]

Problem fixed…

Thanx to all of you, for your suggstions. Some of them may still need to be examined, like the harness issue. But for now the problem was, as suggested by KD, a bad wire connection. Not one of the original Mercedes, but an installation of DRL from the previous owner.

Underneath the fuse box, the two wires from the aftermarket DRL was loose and the connection was so bad, that a lot of heat and probably sparks, had ruined some wires. It took my great indy a couple of hours to localize the issue based on the fault codes and a standard voltmeter. 10cm of new wire and two new wire connections…

By the way, the engine does not run as smoothly any longer, which brings me back to the harness. As soon I can get my hands on an old one, which I can rebuild with new wires, I will do this. But I also suspect that the rough drive might have something to do with the new distributors and rotor, what was installed right before my problems showed up. I bought some OEM’s in Germany. Also the “new” old base unit might have changed the drive parameters in some way. The first thing I did when the problem started, was to look for the OVP (base unit on this car) and exchange this. So back to the old one.

Again, thanx for all the help.

Rud