Some grim reading...

[big x]

Wiring harness disintegration on IL6's and V8's.
I'm beginning to think I wouldn't recommend a Benz
to my worst enemy.

http://users.adelphia.net/~infoage1/complaints_nhtsa_mercedes_wiring_harness_failures_1991_1996.html

adam

 

[Rose Chap]

Not sure I'd get as worked up about this as some. These are cars over a decade old! You'd expect a few parts to be wearing out surely.

 

[nigel cross]

I cant beleive some one could say The crs are 10 years old, so it doesnt matter. There is a serious problem with all Mercs as far as quality control goes, you simply have to read qall the different pages on this forum to se an underlying theme.There should be no issues with wiring on any car even if it 30 years old unless it has been involved in damage to the wiring. Down to bad design and the quality of the parts being used. It looks to me if MB dont pull their finger out they will be classified as the new Lada's.

 

[stats007]

That's common knowledge - mainly affects the M104 engine though seen across the board on early nineties cars. Usually gets mentioned on here when someone is looking to buy an early car.

 

[Subyland]

Indeed it is a common and known problem. And not cheap to solve as the loom cost over £500+VAT...

 

[janner]

Only a problem from late 1993 to mid 1996. It affects all the wiring in the car, not just the engine loom. The engine wiring is just the first to go because it gets the hottest.
I don't buy the excuse either. Mercedes would have us believe it's to do with it being biodegradable but it just happens to coincide with other cost cutting measures introduced in 1993

 

[stats007]

Most replacements looms I've heard of are from '91 - '93. You can have a loom made up with better quality wire for less than MB charge - I know someone who is doing this for the M104.

 

[IanA2]

Most replacements looms I've heard of are from '91 - '93. You can have a loom made up with better quality wire for less than MB charge - I know someone who is doing this for the M104.

Mine was first registered Feb 92. Recently I've had strange happenings. Sometimes when I indicate all the warning lights go on and sometimes the seatbelt warning light flashes in unison with the indicator flasher. Could this be the begining? Might also be sequila to a few mods I've had done ie satnav and b2. As in every other respect it's a very nice car which I intend to keep, I suspect it would be best just changing the loom as it's likely to when and not if it goes. Can you let me have details of the guy who makes them up? Thanks

 

[stats007]

I think it pays to be proactive - he did one where it appeared fine on the outside but literally fell apart when he moved it. As far as I know he just does the M104 as he had an original loom to work from. IIRC you can buy the loom in sections - I'm sure Shude could confirm.

 

[big x]

Not sure I'd get as worked up about this as some. These are cars over a decade old! You'd expect a few parts to be wearing out surely.

The problem is not just the HT ignition leads which do wear out on any car
but all the wiring.Having said that my old BMW 525i 1986 reached 300k
on the original HT leads.Saw this pic on anotherforum,alternator harness...

On a V12 the costs will be endless..

http://v12uberalles.com/throttle_actuator_rewire.htm

Reading through some of the letters in the original post some people
are on their third wiring loom. I'm amazed some here think that's acceptable.
It would appear MB where selling NOS wiring looms for some time to clear
the shelves before sending out the updated parts.
On some rare models wiring looms are not available any more,
they have to be made to order.

adam

 

[big x]

Most replacements looms I've heard of are from '91 - '93. You can have a loom made up with better quality wire for less than MB charge - I know someone who is doing this for the M104.

I have a 104 can you PM me the guys details thanx.

As far as I can tell most models
1990 to early 1996 with non-4 cylinder engines can
be affected.

adam

 

[Satch]

It is not just an MB problem. Other car makers experience exactly the same and it is well known in the Aviation world as a real and potential killer.

Stems form the use of certain plastics which had good temperature tolerances and insulation characteristics so looked perfectly OK for the intended purpose but over time suffered from chemical breakdown. Newer (and it must be said older) materials do not suffer from this so badly.

This is accelerated by exposure to moisture, heat and vibration. Exactly like the conditions found in an engine compartment.

 

[ddentrec]

Frightening...must affect the W210 as well as they get older.

I have recently completely dismantled my 1984 280TE W123: I removed the wiring loom intact and I can tell you that after a good clean it is as good as new with no cracked insulation anywhere.

It is very heavy though and the quality of the terminal crimping and finishing is first class.

Looks like the accountants have been at work after 1992....

 

[Satch]

Frightening.......

Yes

http://www.vision.net.au/~apaterson/aviation/kapton_mangold.htm

 

[janner]

Reading through some of the letters in the original post some people
are on their third wiring loom. I'm amazed some here think that's acceptable.

Replacement looms are okay. There's a mark on the connector end to tell you if it's the improved wires but I can't remember what it is.
On the W124 it's only from the introduction of the M104 up until 1996 (1991 is too early). Many were replaced ages ago either under warranty or as a goodwill gesture (free labour etc)
The thing is the UK is not as hot as some countries so they're failing later.

 

[Birdman]

Encountered a 1993 S600 V12 in which the engine harness had been replaced due to fried insulation.

Apparently, the problem also presented in the E36 for the same reason - under-specified insulation cooking up in a very hot engine bay. AFAIK the problem doesn't present on post '96 cars.

 

[compress ignite]

See Below (in U.S. it's '91 through '95)

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#1

07-11-2005, 01:45 PM
infoage1

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Join Date: Mar 2005
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Posts: 47


MB Wiring Harness Failure
As most of you know, Mercedes has declined to own up to the engine wiring harness defect in the 1991-1996 model years, and issue a "goodwill" recall.

I just called MBUSA, and I am not *to say the least* satisfied by their response.

Following, is a list of OVER ONE-HUNDRED EIGHTY (updated 6-6-2006) reported consumer complaints (and a number of FIRES..!) that I found on the National Highway Traffic Safety Administration (NHTSA) website concerning the chronic engine compartment wiring harness failure suffered by 1991 through 1996 Mercedes Benz automobiles.

This list is not--by any means--meant to be complete, as it only lists those reports that I was able to locate. Note that the first complaint on the list is mine:

http://users.adelphia.net/~infoage1/...1991_1996.html

If your Mercedes has suffered from the same defect (and it will), please call MBUSA and ask to speak to a supervisor at MBUSA who claims to have NEVER heard of this problem:

1-800-FOR-MERCEDES (1-800-367-6372)

In fact, as you read through the list, notice the arrogance by which the consumer is told this same lie, over and over, by MBUSA.

Click the link below to see hi-resolution images of a typical defective MB wiring harness (remarkable pics by gerryvz):
http://users.adelphia.net/~infoage1/...es_images.html

Please file your own complaint with the NHTSA here, and be added to the list:

http://www-odi.nhtsa.dot.gov/ivoq/


edited on 10-25-05 to include model year 1991 vehicles...
edited on 04-22-06 to include model year 1996 vehicles...


.
__________________
Tom -- 500E-040-5/93
MERCEDES-BENZ 1991-1996 ENGINE WIRING HARNESS DEFECT NHTSA COMPLAINT SUMMARIES

Last edited by infoage1 : Yesterday at 01:17 AM.

​

 

[Vlad]

Concur with what Janner states.......the wiring issue is not such a problem in this country as we live in a colder climate.....most owners who have had problems seem to live in the US. Saying that I'm aware of owners over here having to replace the harness, so I suppose age is starting to take its toll, whereas heat was causing a lot of premature failures in the US.

It only effects 1992 (1993 model year, ie October 1992 onwards) to 1995/6.

Its mainly on cars with the M104 engines and M117 V8's, so W124's, R129's, and S Classes

If anybody is ever thinking of buying a W124 E500 or a R129 500 you need to check whether the harness has been replaced as the underbonnet heat does have an effect on these cars even in our climate. If left you run the danger of the harness shorting out and frying the ECU and the Coil packs.

The E500 i used to run, had just had the harness, ECU and Coil Packs replaced when I bought it....cost the owner £3000.00. Had he replaced the harness only the price would have been @ £800......you need to factor this cost in if you are ever thinking of buying an E500 or R129 500.

I have also read that if you find a decent auto electrician, they can re-wrap the effected area's for a fraction of the price of a new harness.