Replacing Wiring loom

[Stevester 500E]

Has anyone replaced the wiring loom that goes from the engine compartment to the inside of the (car dash, etc.)?

I am ponding replacing as much of the biodegradable wiring harnesses as possible.

Curious to find out how many labor hours an MB dealer charges for this job. I would do it myself, but I dislike taking apart the dash, especially not knowing how much of it I might need to take apart.

Anyone done this job? Any comments other than the expected PITA?

 

[gerryvz]

It probably would be good to check the price of this harness first, to see if it actually feasible economically to replace it.

 

[Klink]

Stevester, I have only ever seen this job required on relatively early 140s and V12 129s operated in really hot climates. I don't think it's something that I would fret over with a 124.

Am I wrong? Is anyone out there seeing this as a problem on 124s? Anyone from the deep South East or desert areas of the US perhaps?

 

[Stevester 500E]

I am probably hypersensitive about the harnesses after seeing so many deteriorated ones.
I thought that any loom that is in the engine bay is eventually going to be baked and eventually deteriorate.

 

[samiam44]

Let us know what a harness costs? I think the main harness w/fuse box is ~ $6k.


M

 

[gerryvz]

Let us know what a harness costs? I think the main harness w/fuse box is ~ $6k.


M

Michael -- exactly my point. This is a HUGELY expensive proposition with

a) no real precedent for problems (remember that this harness doesn't get the heat because it's largely behind the inner and main firewalls)
b) no specific identified issues

The main three areas with demonstrated issues have tended to be:
1) the upper wiring harness, often after it's disturbed during other maintenance and/or heat exposure as heat rises in the engine compartment
2) the ETA inner and outer wiring, again often after it's disturbed or has high mileage/heat exposure
3) the lower wiring harness, due to age and heat exposure

Other wiring in the car, while likely of the same generation of "bio-degradeable" wiring mandated by MB and the law at the time, has not shown a highly abnormal level of failure. If paranoia exists about other wiring harnesses, it is probably prudent to disassemble the entire car and remove/replace all wiring at the same time. I cannot fathom the extent of the undertaking this would require both in time and expense.

The part number for the wiring harness per the original question is either going to be 124 543 59 06 (1992 models), or 124 440 54 05 (1993 models), or 124 440 23 32 (1994 models). The list price of these parts is $4,420 (1992 and 1993 cars) or $3,540 (1994 cars).

That's just THAT harness ... of course there are other major harnesses underhood that go through the firewall, such as the headlamp harness ($505 or $515 depending on model year) or the positive block-to-starter cable, which runs $295, or the battery-to-positive block cable, which runs $165.

And then, there's the OTHER harness that powers a lot of the car's internal components, such as the ACC system, radio, seat belt warning, stop light switch, headlight switch, parking brake sensor and TONS of other stuff from the fuse box inward. THAT harness ranges between $2,100 and $2,600, depending on the model year your car is.

Heck, if you're gonna do all that, you may as well do the tail lamp wiring harness too. That guy runs between $1700 and $2,900 depending on your model year.

And the all-critical fuel pump harness? Can't forget that one !!! That's a pretty cheap one ... only $63. Bargain !!

There are many other "biodegradeable" harnesses on the car, but you get the drift. The cost of replacing even just the two or three harnesses that go through the firewall will quickly exceed the GVZ $5,000 DM budget....

Cheers,
Gerry

 

[Stevester 500E]

It sounds like replacing all the harness might cost as much as a garage queen'd 500e/e500 !

 

[gsxr]

Am I wrong? Is anyone out there seeing this as a problem on 124s? Anyone from the deep South East or desert areas of the US perhaps?

I've never even heard of this on a 124. Check the insulation and you'll likely find it is all pristine. Only the engine harnesses (and ETA pigtail) appear to be affected on the 124's.

I wouldn't be surprised if DIY labor for the replacement would run somewhere between 50-100 hours, since a significant amount of the interior would need to be gutted. Those body harnesses spider-web like crazy.

 

[samiam44]

I did one major harness replacement in the 90's. It was a one year old Porsche. Local dealer refused to do the repairs. It was easy due to the newness of the car. Inspected all harnesses for p/n tags ordered parts. Install removed/replaced one connector at a time.
I would guess a few days to do the job. I honestly was thinking the price would be higher. ~$3300 discounted is good. Plan on it taking a few weeks to receive. I bet it will be made to order.


M

 

[gerryvz]

I did one major harness replacement in the 90's. It was a one year old Porsche. Local dealer refused to do the repairs. It was easy due to the newness of the car. Inspected all harnesses for p/n tags ordered parts. Install removed/replaced one connector at a time.
I would guess a few days to do the job. I honestly was thinking the price would be higher. ~$3300 discounted is good. Plan on it taking a few weeks to receive. I bet it will be made to order.


M

Definitely. I look forward to a robust HOW-TO article on multiple non upper/lower harness replacements from the Stevester. When can we expect you to provide?

Cheers,
Gerry

 

[zooklm]

I saw this older thread and wanted to comment. When I purchased my 92 500e (about 10 years ago), it had an electrical short where the 30 amp aluminum blade fuse did not blow and shorted (and melted) part of the harness that goes under the dash and connected to the ignition switch , light switch, etc. I tried to find a good one at the time but was not able to do so. Therefore, I decieded to repair the existing harness because I did not think it was too bad. I ended up taking the harness out of the car to do the repairs and then reinstalled it. It required removing the dash, console, both front seats and kick panels. For wires that ran through the dash, i tied string to the wires to help keep the right routing and end locations. It worked fairly well for many years, but I think the repairs may be starting to fail as I have am having a few electrical gremlins showing up on occasion. Therefore, I am on the hunt for a complete undamaged A124 543 91 32 harness. This is 1992 part, so later years will not work. So if you know of someone parting a 92, please let me know. Otherwise, i will likely purschase a new harness (available for $1600) sometime later this year.
Thanks,
Lee

 

[Stevester 500E]

I don't think this will happen anytime soon.
A master MB Mechanic and V12 enthusiast had told me he has replaced several body harness on W140 V12's.
It made me wonder about the W124 body harnesses going bad.
But apparently, it's not a common failure on W124's.

Definitely. I look forward to a robust HOW-TO article on multiple non upper/lower harness replacements from the Stevester. When can we expect you to provide?

Cheers,
Gerry

 

[gsxr]

... I think the repairs may be starting to fail as I have am having a few electrical gremlins showing up on occasion.

Lee, what exact symptoms are you having for the 'gremlins'? I'd want to be 110% certain it's this specific harness that is causing the problems. Also, how many repairs did you have to make on the original?

Therefore, I am on the hunt for a complete undamaged A124 543 91 32 harness. This is 1992 part, so later years will not work. So if you know of someone parting a 92, please let me know. Otherwise, i will likely purschase a new harness (available for $1600) sometime later this year.

Have you called a dealer to have them check stock in Paragon, to confirm they are really available? All the online websites will show pricing, but that does not mean the harness is available. The 124.034 lower harness has been NLA for a couple years now but most all the interweb vendors still show pricing, and will let you place an order that will be promptly cancelled...

 

[Ruffles]

Hiya Folks,

We did have a failure of the internal wiring harness at a specific location and I would recommend that you check yours as the repair would be far less costly than what it is costing us.

The failure point was the cigarette lighter harness at the back end where the wire is prone to flex when owners keep their key change in the ash tray. The continuous flexing led to the deterioration of ours and I was lucky enough to be at the vehicle when the fire started. After 2.5 minutes taken to isolate the battery, we have had to replace the whole harness, dash board and all the trim surrounding it.

I would recommend that you inspect this area and make sure that you isolate the positive and negative wires in this area so that you are not left in the same position as me.

Regards

Pez

 

[nocfn]

Would you say perhaps to just disconnect the electrical from the ashtray as a prevent?

 

[gsxr]

Hiya Folks, We did have a failure of the internal wiring harness at a specific location and I would recommend that you check yours as the repair would be far less costly than what it is costing us.

The failure point was the cigarette lighter harness at the back end where the wire is prone to flex when owners keep their key change in the ash tray. The continuous flexing led to the deterioration of ours and I was lucky enough to be at the vehicle when the fire started. After 2.5 minutes taken to isolate the battery, we have had to replace the whole harness, dash board and all the trim surrounding it.

Pez, that is crazy. Just curious, did your car have the factory radio / head unit, or was an aftermarket unit installed? The wiring to the ash tray normally should be able to deal with frequent flexing.

 

[jaymanek]

I have just taken the loom out of my American high mileage 500e.. The outer insulation sleeves all crumbled when moved but the wires were all perfect.. it’s a MASSIVE job to pull this loom and replace it

 

[Ruffles]

Hiya GSXR,

Good question. The vehicle was supplied in Germany with an Exclusiv Head Unit and then it was replaced with the narrow frequency Japanese Unit somewhere in the 90's when the vehicle was sent to Japan. The original connectors were preserved and there was no cutting at all.

When we conducted an investigation we found the source of the short circuit was the wires from the cigar lighter ahead of the connector. There were no pinched stereo leads at all. The installation was standard. We could only gauge that the cable was flexed, damaged and then shorted - perhaps heat from the lighter may have been a contributing factor. The resultant damage was incredible and it was surprising to see how quickly the damage spread.

I would recommend that you check the circuit and add further insulation to the area beyond the connector.

I have received two harnesses thus far - a 500E from 1991 and an E320 from 1995. Both of these harnesses are in perfect condition without any degradation as described by others.

I am hunting for a replacement harness or further advice on changes between the years. The part# for our harness is A1244407406. I cannot seem to figure the subtle differences between the harnesses over the years - the HVAC unit appears to be the same through the model ranges and I can only put it down to the switches on the console being different.

The is sure going to be a challenging refit but we will persevere with it so that we can preserve this wonderful vehicle. If we run into difficulty, we will have to manufacture specific circuits for the vehicle.

Any advice would be most welcome.

Cheers

Perry