1987 300E

How hard is it tp replace the engine wiring harness in one of these? I'm a reasonably acconplished amateur mechanic, FWIW.

I saw the DIY article on a different model, and it seemed the guy had a pretty easy time of it.

Thanks,
Jimmy

It can't be hard, except for paying for it. They are actually more expensive than the later ones, but fortunately tend not to be a problem.

It's not bad at all--why are you replacing the harness?

-GH

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The insulation is shot on the wires in the battery area/passenger side of the car. Exposed and corroded wiring, shorting to ground, dead battery, that sort of thing.

Doesn't sound like the engine wiring harness. Can you get a part number off it?

It's dark outside already (no garage for us, unfortunately), and I ain't been feeling good, but I poked around and all I got was this:

The black plastic sheathing is missing in a spot from a bunch of wires that actually terminate in two places.

One group of wires (sheathed at this point), terminates in a female black plug that attaches to a little aluminum-colored metal cylinder about 2" tall and 1" wide, directly in front of the battery. That black female plug has the numbers 011 5457128 on it.

The second group of wires (smaller bundle) in the sheathe plugs into another plug nearby. It has the numbers 012 545 0428 (or 6) stamped on it.

The whole shebang seems to enter the firewall without a plug, just stright through? Maybe? I really couldn't see well, as it was so dark. I'll have to get out there tomorrow and pull out the battery and rectify this info.

Thanks so much,
Jimmy

Maybe it is the wiring harness. I think when you get a price for the part you may want to give some thought to repair. They really don't tend to be prone to pervasive failure in that era, but hard to know what all it's been exposed to in its life.

You mean just replace the bad part of the wiring? I think it's just a short section, but not sure....

That or just recover the wires that are there with heat shrink tubing, electricians tape, liquid electricians tape, plastic loom, whatever it takes to keep the wires from shorting out.

Cool. Thanks so much for the help. There's only a small 3" section that's marred, it seems. I have no idea how it happened. Maybe wearing against the hood? That particular section of the wiring does ride high. I bet it just rubbed raw.

I guess I should have thought of the simpler repair tips a while ago. I tend to be single-minded and sorta dense about certain kinds of logic. Asperger's, I think. But that's another story....

I've used a razor blade to cut through a bit of the black rubber sheathing, and it's one wire, the tan one with a red stripe, that seems to have super-heated and melted its own insulation for a length there, at some points bonding all the other wires (insulation intact) into a gooey single entity. That tan wire even scorched the black rubber sheathing in spots.

It sounds like you've had a short, a blown fuse, and close to an engine fire. I would think it repairable if that's all there is, but that could be a sign that other areas of the harness are suspect. If it was me I'd remove the harness, inspect the whole thing, price a new harness, and then make the call. It is much easier to do a good repair job off the car. It's a tough call - you don't want to risk an engine fire, but I believe a new harness is well over a thousand dollars.

I don't think it's the main harness? The main harness is different from the A/C harness, right? Lord, I guess I could buckle down and pay the $1,000.00 if it's all the same harness, but wow that's expensive. And it does seem to be two different harnesses....

One of those black plugs, the one that attaches to that 2"/1" metal device, is connected to the A/C system (I think), the hoses that disappear into the firewall towards the part of the A/C system behind the dash (condenser?). And the other end of the wiring harness disappears directly into the firewall. And that whole length of harness is just a melted mess. I don't know if could sort it out.

I'm gonna haul out my CD-ROM manual and get to the bottom of this. I have to wait until my wife gets home, because she has the PC laptop.