Another 124 wiring harness question
 

Prior threads indicate that replacing the engine wiring harness on the 6 cylinder models should take about two or three hours. How long should the replacement time be for the 1994/1995 E420 models?

Also, how long should it take to replace the wiring harness that connects to the alternator on these V-8 models?

I replaced the main engine wiring harness in my 1993 400E in about 1.5 hours. Its not a difficult job but it does take a bit of thought figuring out how certain parts of the harness come apart.

I've not replaced the harness that controls the alternator - can't comment on that one.

Tim

Tim, may I ask what were the symptoms that led you to inspect and change your wiring harness?

enjoy your drive, timreid

timreid

I had heard about engine wiring harnesses failing due to faulty insulation so I decided to inspect my harness. The classic symptoms are intermittent check engine lights end EA faults causing the drive by wire throttle system to go into limp home mode. My car was not exhibiting any of these symptoms but inspection of the harness showed lots of failed insulation and several 3-4 inch lengths of BARE WIRE. Given the condition of the harness I was amazed the car ran at all.

The replacement of the harness did solve one problem I had been having - at idle the engine would sometimes stumble a bit. Almost like it was losing a cylinder for a split second. With the new harness installed the idle is a smooth as glass.

Tim

The replacement of the harness did solve one problem I had been having - at idle the engine would sometimes stumble a bit. Almost like it was losing a cylinder for a split second. With the new harness installed the idle is a smooth as glass.

Thanks Tim, my 400E seems to be experiencing the same problems as your 400E did. I'll inspect the harness this weekend, any tips on inspection and installation, and I was wondering did MB help you on the harness cost?
enjoy your drive, timreid

Yes, thanks Tim! My 400E has the exact intermittant "stumble" at idle from time to time. Also I've had the "limp home" situation about 3 times in the last few years. I think I'll have the harness replaced first and see if that cures the problem (before investing another $1000 + for a new throttle body).

Why?
 

I was at the Dealership today (I would rather be at the dentist!) since I needed a Cap, Rotor and Plugs for my 84 280CE.

As I stood waiting for the parts guy to look up the cap, I could hear a service adviser giving an owner the bad news about needing a new wiring harness, $800 "their price" I think he was meaning wholesale, plus labour. I didn't hear what year or model, but I stood their thinking about all the times I have seen this issue here.

My question is, why hasn't there been a secret warranty, recall or even class action law suit over this issue?.

Anyway, they could not locate the part # for a cap?, kept bringing up the rotor # instead, so the guy had to make a call. I don't know why, but they don't seem to work at the counter at the dealer here, I think it's just for show (actually a MB boutique really) since they go into a back room to do stuff. I don't like that, I want to know who he's talking too, and what he's asking. Well finally he came back with a Cap and Rotor. 'That will be $99.00 for the cap and $20 for the rotor! oh and we are out of plugs!" WTF is that all about.

I conveyed my displeasure at this development, especially the price, so he says 'Here I give you a MB shopping bag for your parts", yeah like I'm impressed. How can a dealership who has been voted (by who I wonder?) best dealer 5 years in a row, give such consistent bad service. At least they don't get my repair business anymore.

Crownwayne,
Do you see why we love Fastlane? No annoying trips to the dealer, better service, better price. Just have to plan ahead since it'll take a couple days to receive parts.

The quality of the parts people varies significantly from dealer to dealer. Some of the guys (and girls) are very, very good - some of them are not so hot. The marketplace will decide who wins, buy things from the good guys and avoid the bad. To me its worth spending a few extra $$ if the person behind the counter is good - you are building a relationship and the parts guys can be incredibly helpful at times. That said I would not pay $120 for a cap and rotor for a 84 280....

I paid $418 for the harness from the MB dealer - it was a wholesale price, I don't have the list price. Part number was 124-440-19-06. I think fastlane has them for $475 or so.

Install is prety straightforward. Layout the new harness on the engine and see where all the wires go - then figure out what the things you have to disconnect to make it all happen. Don't be intiminated by the number of wires and connectors - its not as bad as it looks when you take the new harness out of the box. Most of the connections go back to the main engine ECU so I did disconnect the battery before starting - I think this is recommended in the MB service manual but I can't remember.

To inspect the old harness cut a small slit in the plastic covering and take a look at the wires. Be careful not to cut the wires under the plastic sheathing. If the wires are bad you will see a powder that is the old insulation and lengths of bare corroded wires inside the harness sheath. Its pretty obvious. You should also check the wires that go to the EA motor that controls the throttle valve. My EA motor had been replaced prior to my ownership and the wires were fine but I have also heard these wires also can fail.

This is not a tough job - I would rate it about a 3-4 on a scale of 10.

Tim

Tim - Thanks for your replies. Phil at the PartsShop has the 124 440 19 06 wiring harness for $405.50 before shipping.

Does anyone have a clue about why the Mercedes service departments still claim replacing the engine wiring harness is an 8 hour job?

Also, has anyone tackled the alternator wiring harness and if so, how long does that one take?

Thanks for the advise 400E (Steve), but isn't FASTLINE only available to the United States?, also I have to admit I usually do these things on impulse. If I plan it, it never gets done at all.

MB book time on changing the 500E upper wiring harness is 2.5 hours (just had it done @136K mile). 8 hours is way too long, and expensive, for any R&R of a wiring harness that's basically plug and chug!! I was going to do this myself but my aftermarket warranty footed the whole bill. Like Tim says...its not too hard to DIY should you choose to do so.

Dealers pay under $400 for the 500E upper harness here on the East Coast....seems reasonable for a part that's like a spinal cord to the car. :D

I just did mine earlier this year at around 110K miles or so. $335 or so at wholesale from the local dealer and the work is not difficult.

Mine looked OK and the car ran great but the insulation on individual wires inside the harness was shot and you could see bare wires in many places. If you never move the harness it may last a while but if its ever moved for some other repair watch out!

The hardest part of the install for me was getting the plastic thing that goes around the wire bundle where it goes through the firewall (between the engine and electronics) back in place. I broke the original one at the hinge and had to order a new one. I'd give myself a Saturday afternoon to get it all done. Depending on your mileage, you might want to visit breather hoses, vac lines, MAF gasket and any other plastic/rubber bits since you're already in there.

Randy
'94 E500

We just recently bought a W124 diesel. Is this wire harness that everyone is talking about, on my '87 TD?

Yep, I didn't realize that before. Looks like PartsShop, however, will do international orders.

If nothing else, you might use them to buy a half dozen oil filters, some windshield wiper refills, etc. since you know you'll use these things eventually.