Donnie, MBDoc, others....do I need to replace my harness?
 

I picked up my 500E from the shop today after having some minor imperfections with the paint job taken care of...

Upon starting the car, it seemed like it was sputtering. It went away after i left it idling 'til it reached operating temps (around 85 degrees). After driving it for a while, and upon getting caught in stop and go traffic, I noticed that:

(1) some lights on the dash which weren't supposed to be lit, were (i.e. a/c louvre wheels, seat heater controls, window controls--i think, don't clearly remember--and some others)

(2) engine was sputtering again, but was okay after 2000rpm or so...taking off from a stop was difficult as a result, but was okay once under way

(3) idle was erratic, almost threatening to shut off at times

(4) tach was erratic, moving from 500rpm to around 1500 (couldn't recall if engine speed was in sync with tach movement--I was too freaked)

Upon getting back to the office, after trying to look for the culprit, I noticed that unplugging the harness from the coolant (blue) sensor (the one that would make the aux fan run continuously if you unplug it) everything went back to normal. Car was running fine, idle was normal, dash lights were off. Drove it for an hour and everything was fine (well, except that the fan was running the whole time).

I'm suspecting either the OVP due to the erratic idle but have stronger suspicions with the engine wiring harness (124 440 20 06).

What do you guys think?

Also, how involved is the wiring harness replacement? The reason I ask is that I know of no one in this country familiar with the 500E (as there are only 2 here). Is this a job strictly for the dealer (which will cost me upwards of $1200 in parts and labor) or can I just pick up the harness from the Parts Shop and have an independent do it? (the dealer only works with dealer supplied parts, some independents here are flexible, especially with expensive parts).

Eagerly awaiting your replies...

If you KNOW the harness has failed, I would replace it soon! The thing is, we can only get parts for the USA version of the 500E. Is your car a US version?

The part number of that harness is the same as a US version. 124-440-20-06 fits only W124.036 cars from 1993. US list is $400.
The harness should take 2.5-3.5 hrs to install.

Cool! Thanks DOC. Well, I guess we can get it for you. Just call Phil at the 1-888# and get it coming to you!

I already checked with Phil and he quoted be a bit less than that (I've been very good customer! :D))

My car is a Canada spec 500E, btw.

How do I know for sure the harness has failed? Are the symptoms I described indicative of a wiring harness failure? Any other guesses? I wouldn't mind replacing parts I may need to have replaced anyway (as long as they're not too $$$!).

I have a little less than 40K mi on the odometer...I've checked the records and the numbers check out.

Thanks again!

did you consider checking/changing the temp sensor you refered to?

The sensor (and most of the other sensors in the engine bay) were replaced around 2 months ago...

Check ALL connections! Seems strange that the problem would surface as it has.

Good luck!

the sensor still looks suspicious...even just a couple of months new..and although I'm not even to the doesn't know what he's talking about step let alone expert I read this web like the morning paper and from what I've read the wiring harness is a degredation as the result of exposure to high heat over long periods of time and I'm not sure if 40,000 miles is enough to indicate that...

Actually, I was thinking that when the problem first popped up. Slowly though, I'm beginning to think that eight years is still eight years. Time does weird stuff to different things.

I forgot to mention, the wire connecting to the plug that connects to the harness is brittle and frayed. No, it's not shorting out, at least where I can see it...but who knows what the condition is under the wire looms!?!

I'm ordering them as soon as I hear back from Phil...

I remembered same thing happened to my W210. Try changing the battery. For me, it is the weak battery that causes havoc to the system. The meters swing eratically upon starting and engine sputters, I was always scared of the engine stalling at traffic lights. After The battery change, every thing went back to normal.

However, I did change my wiring harness, but after 3 months later. As I discovered that the insulating sheaths are broken and chances of washing the engine is going to blow up the electronics.

The other day, my exterior side mirror did not work and fuse kept blowing. I opened it up and found all the 6 wires bare. No sighs of the PVC sheathing. If I were you, I keep a look out.

Hope this helps