Just figured I'd post a bit on info on the upper wiring harness on a 92 400E. I replaced the harness roughly in 2004 - the tag on it looks to show a 2003 build date (bought the new one from a mercedes dealer in CA). Anyway as the car is now a parts car I figured I should take the harness out. Well the new one does not seem to show any signs of cracking on the exposed wires. However, the double insulation over the fuel inj connectors and front engine connectors is quite hard (more so than the old crumbly one which I still actually have around). While I don't believe this will cause any failures it is interesting that they upgraded the wire but may have gotten a less than optimal solution on the extra insulation.

Paul

So you're saying the new wiring harness held up but lost its flexibility over time?

__________________
TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth

Yes - the exposed wires are still fine. The example is the ground wire that has a fair amount just single insulation and. That wire is still nice and flexible, I just took a look and the old one is crispy breaks and cracks when bent. The secondary insulation, for example on the cam sensor connectors, is now quite stiff.

Paul

On almost ALL cars, the wiring harness WILL get "stiff" due to constant heat cycles.

The old "bio stuff" didn't get as hard do to the type of plastic coating used.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

I just found out that my 92 400e has the old original harness (I think). I was having a problem with the aux fan being on all the time when I found that the two wires going to the two-prong temp sensor were completely bare under the outer balck sheathing, and touching each other. I could really use a used harness in OK condition.

__________________
1992 400E current
1988 300E sold
1973 280C totalled
1973 280SEL never got it running
1971 250C my first love but rusted out

Sorry I'm not planning on selling the spare at this time as I picked up a new to me 400E of identical vintage (92). The PO stated that they went through and rewired the harness that is in there now (so did the strand by strand replacement rather than spend $$$ on new) so I'd rather keep the spare as a possible and likely swap into my current 400E.

However I do have the dead one that came off my first 400E back in ~2004 if you want to take a crack at rewiring one yourself. I think I cut off one of the connectors - round 2 or 4 pin when I was checking the condition of the insulation - I'm not sure if I can locate that one but you could get 90% done before you cannibalize your current one.

mbdoc - I realize most any harness will stiffen up due to heat/environment, just found it interesting and maybe a point to remember that if you pull a harness and the secondary insulation is stiff - it MAY be updated.

Paul

I wouldn't mind taking a crack at it-I just got a new soldering iron. My 400e has 266,000 miles on it, so I don't want to spend alot of money on it. I find it unbelieveable that my car has the original harness after all this time and miles. Afraid to cut into it further until I have a replacement.

__________________
1992 400E current
1988 300E sold
1973 280C totalled
1973 280SEL never got it running
1971 250C my first love but rusted out

I'll give you the old one for the cost of shipping. Let me take a look tonight and see what the long dimension is (if it will fit in a flat rate box) - the plastic piece is the limiting factor. I'll also take a look around if I have the one connector I cut off.

Will send you an email
Paul

92 400e's don't suffer from the messed up wires, nor the plastic oil tubes..

if the connector to the thermosensor is disconnected the fan will be on all the time (sensor painted blue near thermostat).
(or of course if its bad)

but wire harness repair isn't that hard unless its completely gone to crap check out my thread, and becareful with the knock sensor wires especially.

Gazbor - absolutely wrong on the harness (I think you are correct on the oil tubes, I can pull the covers on the parts car if anyone wants to see).

1992's do in fact suffer from crispy harnesses. I don't know why people continue to state otherwise. I will take pictures tonight and post those, hopefully that will end people stating 92's don't have the issue (probably not but at least there with be evidence that the problem exists on a 1992 wire harness).

Paul

If you are using windows, try this:

Click on the below thread and hit the Ctrl and F keys (not sure about Macs, but I know they have the same search function). Then type 400E or 1992 in the search box--I stopped counting after about six 1992 400E reports.

If you are bored, try search words "fire" "flames" "smoke" "burning" and the like:

MERCEDES-BENZ 1991-1997 ENGINE WIRING HARNESS DEFECT - infoage1

__________________
MERCEDES-BENZ 1991-1997 ENGINE WIRING HARNESS DEFECT NHTSA COMPLAINTS

Because they read it on the internet. As Mark Twain said a lie can travel half way around the world while the truth is still putting on its pants. 1992 400Es do have a different part number than later 124.034s but they are just as prone to fail as the others.

And my 1992 400E is proof. I'm afraid to shut the hood too hard the way those wires look.

__________________
1992 400E current
1988 300E sold
1973 280C totalled
1973 280SEL never got it running
1971 250C my first love but rusted out