Sorry Another S500 Wire Harness Question. - PeachParts Mercedes-Benz Forum

Targa-NF · #1 09-07-2012, 08:57 AM

Hey everyone. I know this subject has been beaten to death... And is a sore spot for a lot of us. Anyway I have just added a 1992 S500 to the fleet and she has a few issues with SLS and wire harness.
My question is with the harness. Is the wire problem mainly on the main engine harness "part# 140 540 1132 " or can it most likely the whole car wiring? And what about the rest of the " under hood " wiring?
Why I ask is because she is acting different then my C280 wire harness failure. The C280 just had running problems. But The S500 has no speedo, and when its raining every now and then all the gauge lights will flash and my seat belt light will start flashing like i just started car. The car runs very nice and smooth. No missing or any other sign of harness failure. Plan to dig into harness and have a good look at all wires when it stops raining. Its been Pouring for passed few days

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I know I should check out all wires before asking questions. But just wanted to hear what other people have found and any tips they might have.
Thanks. Jay

tecqboy · #2 09-07-2012, 09:53 AM

I thought that 1992 was before the engine wiring harness issue, maybe wrong. But I'd check for a problem in the VDO, possibly the "bad capacitor" issue. Spray and clean the VDO plug contacts with contact cleaner.

MAVA · #3 09-07-2012, 10:48 AM

Targa,

In my opinion it is where it is exposed to the elements-Heat and light...

My 1996 S320 does not have the problem in the engine compartment, but sure has it in the mirrors. The test is :

Fold the mirrors from the button near the shifter if they stop half way. It is because the wiring is shorting together, and the fuse has just popped! Look at the folded mirrors for exposed wiring. If the mirrors fold and come back, I would not worry about in the mirrors.

86560SEL · #4 09-07-2012, 12:49 PM

Quote:

Originally Posted by Targa-NF

Hey everyone. I know this subject has been beaten to death... And is a sore spot for a lot of us. Anyway I have just added a 1992 S500 to the fleet and she has a few issues with SLS and wire harness.

Are you sure its a 1992? The "S500" name didnt roll around until 1994. I am guessing you either have a 1992 500SEL or a 1994-95 S500.

Quote:

Originally Posted by tecqboy

I thought that 1992 was before the engine wiring harness issue, maybe wrong. But I'd check for a problem in the VDO, possibly the "bad capacitor" issue. Spray and clean the VDO plug contacts with contact cleaner.

Yeah, I have heard alot of problems are not uncommon with the early W140. Thankfully the '93 I am hopefully getting already have the replacement upgrade from the dealer. I have heard that the very early '92 models (made in late '91) didnt have the wire harness issues, but I cant say for sure. I know my uncle has a '92 300SE (W140) that was made in late '91 and he has never had a wiring harness issue and its never been replaced... they bought the car new.

Quote:

Originally Posted by MAVA

Targa,

In my opinion it is where it is exposed to the elements-Heat and light...

My 1996 S320 does not have the problem in the engine compartment, but sure has it in the mirrors. The test is :

Fold the mirrors from the button near the shifter if they stop half way. It is because the wiring is shorting together, and the fuse has just popped! Look at the folded mirrors for exposed wiring. If the mirrors fold and come back, I would not worry about in the mirrors.

Thats aht I have heard as well. I dont think that the 1996 had the bad engine wiring harnesses, I think that was the first year of the change. However, I think that wiring stayed in the mirrors on all of them up through '99.

Pili380SL · #5 09-07-2012, 02:56 PM

That sounds more like a cluster issue to me as well. See if a light tap on the dash directly above the cluster changes the symptoms or causes a flicker.

Gilly · #6 09-07-2012, 06:29 PM

Cluster issue a possiblity, could also be a wheel speed sensor, do you have any other warning lights that are on constantly (ABS or ASR)?
Could also check fuses in the Base Module.

Targa-NF · #7 09-07-2012, 06:49 PM

She was built in 03/92. And it has S500 on the trunk. Might be different with Canadian models. Does anyone know when the bad wiring started?

I have not had a chance to look at wiring yet. Was pouring all day again today.
Going to be nice tomorrow. Going to dig in and see what it looks like. I also gave a few smacks on the dash, but speedo did not move.

Does the VDO just pull out like the older Benz's ? And how can I test it?

Thanks. Jay

Targa-NF · #8 09-07-2012, 06:53 PM

Both ABS and ARS are on. Was going to test speed sensor and see if ABS sensors need cleaning. All fuses are good as well. Roy said I could spin tire and get voltage from speed sensor if working right.

Thanks. Jay

86560SEL · #9 09-07-2012, 07:30 PM

Quote:

Originally Posted by Targa-NF

She was built in 03/92. And it has S500 on the trunk. Might be different with Canadian models. Does anyone know when the bad wiring started?

Oh yeah, I forgot you were in Canada. They may have started using that trim name up there first. I know many cars that were the same had different names up there. Here, the S500 didnt come out until late '93 as a '94 model. We had "SE" or "SEL" after the numbers on the 92-93 S-Class sedans here... the SE was ther shorter wheelbase model and the SEL was the long wheelbase mode, but they were the same car, no changes that I am aware of until the '96 or was it '97? freshening.

Hopefully someone really smart on these cars and tell you about the wiring harness year. I know my uncles was made in late '91 and has had no problems, but the '93 400SEL I am about to purchase was made in 11/92 I believe and obviously had the bad wiring harness, as it was replaced in 2001.

Good luck!

Gilly · #10 09-07-2012, 11:43 PM

IIRC there is only one wheel speed sensor that is used for the speedo. Easy way is to get a scanner to check all the wheel speed signals. Again going by memory I think it is the left front wheel speed signal that is used, but is definitely a front.
The fuses i am referring to are in the BASE Module, this is kind of ditched in the rear of the engine bay on the passenger side, there is a window on top with a row of fuses. You will likely need to remove a section of covering just to see it. You also may have an addition cover held down by allen screws just to get in to the module box. You will see rows of modules, again the base module has a window you open to get to a row of "American-looking" fuses, not the ceramic ones we are used to on MBs of this vintage. Check those fuses. There will be empty fuse positions, that is normal, just check the ones that are there for blown fuses.
If you haven't check the BM fuses, do that first. A blown fuse in the BM could be causing the speedo to be inop and the ABS/ASR lights to be on, this can cause many various seemingly unrelated problems.
The cluster does pull out like the other chassis of this vintage. You have to be VERY VERY careful because if you tools slip off you LIKELY will chip off a section of the cluster lens and bezel when it slips.
Is this the mechanical odometer or digital? I know very little about testing the cluster. Is the odometer advancing when you drive the car or is the odometer dead too?
Here is a pic of a cluster I found online, at the right is a broken lens, this is what happens if you are careless removing it:

Targa-NF · #11 09-08-2012, 12:41 PM

So the harness directly on the engine has the cracking wires, but the rest of the under hood wires look good.... For now....
So I'm going to get a new one.
I checked out the base module fuses and they are all good. Going to try and get her in for a scan and see if they can find anything out that way. Is there anything else i can check?
Thanks. Jay