Hi

I've just been reading some horror stories on mid 90s W124s cars going up in flames due to the infamous wiring harness failure. I have a 95 E300D. I would like to open up and check in the critical places to see if my insulation is deteriorating or not .

Where are the most likely points of failure so i can check them first to detect if there is a risk of catastrophic failure?

Keith

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Keith

1995 E300D auto Wagon

Please, where did you find the stories?

i just searched on words like smoke, flames, wiring, W124 etc on this and other MB forums. I dont think there are lots of instances but if this is a possibility of a failure mode that could occur then i'm for checking out things on safety grounds.

Keith

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Keith

1995 E300D auto Wagon

While replacing glow plugs I noticed that the wire insulation had failed on one of the glow plug connectors. Upon closer inspection I found insulation failures at a bunch of the connectors coming from the harness. Insulation gets stiff and then appears to just fall off over time. I replaced the harness just to prevent any electrical problems down the road. I had not had any up to that point. Replacement was not a bad job since I already had the intake off, but was expensive, although not as high as a gasser.

Good luck

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Bill Brune

86 190D 2.5 5spd 314k
87 190DT 150k
87 300SDL 357k
95 E300D 115k
02 Jetta TDI 90k
99 Subaru Legacy

I heard the petrol models are more prone to this - the harness directly above the engine starts to disintergrate over time.

I've had a poke around what wires I can see and get to without taking everything apart. Thankfully I couldn't see anything bad apart from one connection which I fixed with some electrical tape.

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1993 320TE M104
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past:

1983 230E W123 M102
1994 E300D S124 OM606 (x2)
1967 250SE W108 M129
1972 280se 3.5 W108 M116
1980 280SE W116 M110
1980 350SE W116 M116
1992 300E W124 M103
1994 E280 W124 M104
----------------------------------------------
"music and women I cannot but give way to, whatever my business" -Pepys

Bill
i sort of feel inclined to do likewise. Mine has only 170k miles on the clock so I am hoping for many more years service.

How much did your harness cost?
was it from MB dealer?
How long did it take and did it require removal of the dash ?(again ! )

thanks for responding to my post
Keith

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Keith

1995 E300D auto Wagon

In my '95 E300D The wiring harness was completely gone in basically Four Locations.

1) The wires leading to the temperature sensor (Top front of engine) controlling the Auxiliary fans.

2) Back of Battery, behind black plastic cover. That was the worst place. Wires actually caught fire there.

3) AC Speed sensor wires.

4) Some other wires that only becomes visible once you remove the cross-over pipe.

I managed to repair all damaged wire segments by splicing in new wires. and shrink-wrapping them. Its been about a year now, and so far so good. I am sure however that I'll have to change the complete harness at some point.

Phil

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'95 E300 Diesel, 264,000 Miles. [Sold it]

Thanks Phil , just what i needed . will do some careful examination at the weekend.

Any time/cost estimates for the harness replace?

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Keith

1995 E300D auto Wagon

in addition the wires under the crossover were connected to the flap controllers.

As far as cost goes, it was around $375 as I recall. I consider repairing it, but since I could not inspect the condition of the insulation where the wires were bundled, I just gave it up and did the replacement. It is not really a bad job, especially if you have the intake off anyway. As a side note, when the plastic fuel lines start seeping, replace the whole lot and save yourself a lot of time and frustration.

I had the new harness all installed when I realized I had one spare connector and nowhere for it to land. Looking at the old one I found a spare line had been clipped just at the edge of the plastic wire loom. Being the cautious sort, I put the engine back together and made sure nothing acted odd before I gave the extra one the snip.

Good luck

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Bill Brune

86 190D 2.5 5spd 314k
87 190DT 150k
87 300SDL 357k
95 E300D 115k
02 Jetta TDI 90k
99 Subaru Legacy

Bill, as I said in my post, I'll have to bite the bullet soon and replace my wiring harness as well. Can you provide a bit more details on the process that you went through. Specifically:

a) How long - start to finish?
b) What needs to be removed/dismantled in order to gain access to all the connectors.
c) Can all the work be done from above.
d) What was the hardest part?
e) Any surprises?
f) What is included as part of the main wiring harness?
g) Does anything else need to be purchased separately?

Any other advise that you can provide will be much appreciated.

Thanks

Phil

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'95 E300 Diesel, 264,000 Miles. [Sold it]

Phil

a) How long - start to finish?
The actual harness took me maybe 1/2 hour. It is all the other stuff that eats up time. I would guess I could do the whole thing in 2~3 hours, after doing it.

b) What needs to be removed/dismantled in order to gain access to all the connectors.
Battery, plastic shield behind it, plastic parts over to the windshield wiper. Intake manifold.

c) Can all the work be done from above.
Yes, no groundhog work, unless you drop something.

d) What was the hardest part?
Nothing in particular.

e) Any surprises?
Just that extra unused (at least in my case)connector in the wiring harness

f) What is included as part of the main wiring harness?
Just the harness, however I did not realize ahead of time that it includes the plastic wire tray. I was really dreading the job before I looked at the replacement. It just snaps in and you are ready to do the connectors

g) Does anything else need to be purchased separately?
Need some small cable ties. As I recall, there is a wire that is attached to the outside of the plastic wire loom. It just takes 3 or four of them.

Any other advise that you can provide will be much appreciated.
I clipped off the wires(leaving a 2~3 inch pigtail) going to the individual glow plugs, and other sensors on the A/C, head and switchover controllers on the bottom of the crossover. After I had the new harness in place I just took off the old connector and put on the new one. Some connectors are keyed, so pay attention. Worked out well, and I could account for all of them easily. Just take your time, look at the new harness before making a move on anything. It seems a bit daunting at first, but really is pretty simple

Bill

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Bill Brune

86 190D 2.5 5spd 314k
87 190DT 150k
87 300SDL 357k
95 E300D 115k
02 Jetta TDI 90k
99 Subaru Legacy

How many gaskets involved in the intake/crossover area? Does the intake gasket need to be replaced or can the old one be reused?

Hi Bil,

Thanks for your reply.

In your response to my question no b), did you actually mean that the intake manifold has to be removed, or just the cross over pipe. Can this job be done without removing the intake manifold?

The reason I am asking, is that I feel comfortable doing it, as long as I don't have to remove the intake manifold. If the intake manifold must absolutely be removed, than I will have my mechanic do the work.

Thanks

Phil

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'95 E300 Diesel, 264,000 Miles. [Sold it]

Bill ,
your input is really helpful thanks

one final question - are there any alternative sources for new harnesses or am I right in assuming its a trip to my local MB dealer?

Keith

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Keith

1995 E300D auto Wagon

Connerm - only actual gasket is where the intake manifold bolts to the head. The cross over is connected on both ends with o-rings. I reused my o-rings, but did put on a new intake gasket.

Phil - the intake has to come off, no other way to get to where you need to be. But honestly it is not a bad job, it also gives you a chance to get the entire manifold cleaned.

Keith - I do not know what to tell you over there in the UK. I did NOT buy mine from a dealer, but rather a local fellow that gets a pretty good cut off the prices. I know here that both fastlane & Rusty can get these harnesses.

Before I forget, it you try the intake youself, be prepared to replace the little plastic parts that connect the egr to the intake. Chances are they will break apart when you pull the tubes out, and they are probably leaking anyway. The little plastic peices are cheap. If you do take the intake off, pls put little rags or towels in the the intake ports, just in case. No one needs something jumping down into the head.

Bill

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Bill Brune

86 190D 2.5 5spd 314k
87 190DT 150k
87 300SDL 357k
95 E300D 115k
02 Jetta TDI 90k
99 Subaru Legacy