Wiring harness repair

[everlyne]

My 1992 W140 wiring harness insulation has gone brittle. I would like to replace the wire. The engine compartment is pretty hot. What sort of wire should i used? I believe i need wire which is resistance to heat, chemical, oil, etc. Please advise what type of wire should i used.
Thanks in advance guys. Appreciate your help.

[wbain5280]

Here's a good site:

http://v12uberalles.com/index.html

and here's a good article:

http://v12uberalles.com/AMM_rewire.htm

and another one:

http://v12uberalles.com/throttle_actuator_rewire.htm

[deanyel]

119 motor or 104 motor? A 92 104 motor isn't known for having problems. Marine wire is probably the toughest that you will find - at any good marine store.

[rchase]

Mercedes makes a replacement harness for your car. If you plan on jury rigging it you might as well sell it and get a Honda to modify to your hearts content.

[lkchris]

Originally Posted by rchase

Mercedes makes a replacement harness for your car. If you plan on jury rigging it you might as well sell it and get a Honda to modify to your hearts content.

Absolutely!

Originally Posted by rchase

Mercedes makes a replacement harness for your car. If you plan on jury rigging it you might as well sell it and get a Honda to modify to your hearts content.

IMHO, a capable person can make up a usable and durable harness. I don't know if I would call that jury rigging, though a purist might.

Anyone can stroke a check for a new harness, but someone who is capable of making a new harness and drives a W140 is looking for a challenge and trying to upgrade the car. I doubt if they are doing it to save money, because their time is worth more than the cost of having a grease monkey install a new one of dubious quality.

[fcicco]

I repalced the wiring harness on my 1995 SL500 (Similar Engine) after the dealer quoted me $1600 for the new harness. (No Labor) He assured me that it was made to the same specs as the origninal harness. There are many comments the subject on this and other forums, so I won't comment further and let you decide on the quality and merits of this particular Mercedes part.
I found the job quite easy. I used Belden 656702,18 AWG Style 1569 - Rated at 105 deg. C. This is a common oil and gas resistant CSA approved wire. (Slightly larger than orginal). Marine wire is a good alternative but get the UL or CSA specs on-line first. I reused all injectors and connectors by carefully soldering/heat shrinking to the new wire.
The key to the job is to get a schematic ( ALLDATA DIY ) and a good ohm-meter and spend an evening planning - marking and preparing. I did this on a Thursday night(3 Hrs) and did the job Friday night (5 Hrs). I cleared all the codes and went for a ride. I did this in early June. There are high temperature wraps available from places like McMaster Carr which I purchased but did not use. I went the summer watching the harness and measuring the wire temp. after long drives in 90 deg F plus heat. The wire never got above 70 deg. C. I will add the temp wrap next spring.
Easy job - under $30 - Engine runs great. E-Mail for Pics and more details.

[lkchris]

Originally Posted by John Holmes III

Anyone can stroke a check for a new harness, but someone who is capable of making a new harness and drives a W140 is looking for a challenge and trying to upgrade the car.

Problem is, it WON'T be an upgrade.

[deanyel]

Originally Posted by rchase

Mercedes makes a replacement harness for your car. If you plan on jury rigging it you might as well sell it and get a Honda to modify to your hearts content.

FYI, Honda makes replacement parts too. This wouldn't solve the problem - he'd just start modifying the Honda. I'm skeptical of this theory that repair methodology - first class versus compromise - should be based on the original price of the car. A car that has no market value has no market value and should be treated accordingly. What it cost originally isn't really relevant. Of course some of us just think building a wiring harness would be great fun - Mercedes or Honda.

[rchase]

Your not "upgrading" the car. Your making an inferior wiring harness that will look bad and may cause unexpected problems with the car. If you can't afford to fix your car correctly and balk at the price of parts why not look at a cheaper car? Would you stick a VW bug engine into it if you threw a rod? Maybee a GM 2 speed transmission if you needed a transmission rebuild?

Im far from a purist but if I opened the hood and saw some cobbled together wiring harness under the hood the first thing I would do is shut the hood and leave. Your absolutely killing the resale value of your car that way. Many of the people who specifically look for 140's know 140's so your market would be first time MB buyers that did not know what to look for.

The new wiring harness is a different kind of wiring that does not break down over time. If you want a real scare just wait 5-7 years when the wiring harness on the inside of your car starts to break down

[rchase]

Originally Posted by deanyel

A car that has no market value has no market value and should be treated accordingly. What it cost originally isn't really relevant. Of course some of us just think building a wiring harness would be great fun - Mercedes or Honda.

Its fortunate that you never owned a classic SL or vintage Rolls Royce or Ferrari. ALL cars go through a period of depressed value. You know those $100,000+ SL's you see at the car shows? They hovered around the 5K mark for a while before their real value was discovered. Those Multi Million dollar Ferrari's did the same. While its unlikely the 140 will ever see any real collectable value you never know what the market will do. The value may eventually rise as the market learns to appreciate its build quality because of the absolute crap thats being produced these days.

Butchering a car because your too cheap to pay for replacement parts is a really sad thing to do. If you want to tinker go build yourself a heathkit tv or something as you might learn something in the process. Putting cheap replacement parts on a car is not the greatest thing in the world but its leagues better than what your planning. By the way guys have you done all the calculations on the resistance changes your harness will cause? Do you have a schematic of the car so that you can use the correct guage of wire and wiring that will take the amperage? Found a solution to provide the same RF shielding that the original harness provided? Price some of the computer modules for your car before diving into your project and decide if you want to spend the money in the event that you connect a wire in the wrong place. Theres a lot more to the process than connecting a bunch of wires with wire nuts in your garage.

[Tomguy]

Holy flaming and ignorance, Batman!

Some people may find it hard to do a harness properly. Others may not have the tools to do it properly. Still others would not hesitate to spend money on a new harness which may be as bad as the original.

Personally, if I bought a 124 and the harness went bad, I'd do a new one myself. I know how to solder, and I've done harnesses before - I even did them for the wires in my PCs because it looks so much better. Not everyone with a soldering gun can do a good job, but if the wire is the same (or better) quality of the original AND you take your time to do it, you can easily make a harness that looks BETTER than the original.

Besides, I think it'd look cool to have a graphite 500E with a graphite-colored harness under the hood

[deanyel]

I think the flaw in the logic here is the assumption that these cars are going to be on the road a long time and bought and sold by future owners. The reality is these cars are going to the salvage yard way sooner than any MB that came before them. It's a waste for them to arrive at the salvage yard with lots of shiny new parts. The idea that you must always buy expensive new factory parts just accelerates the date of their economic obsolesence.

Originally Posted by deanyel

I think the flaw in the logic here is the assumption that these cars are going to be on the road a long time and bought and sold by future owners. The reality is these cars are going to the salvage yard way sooner than any MB that came before them. It's a waste for them to arrive at the salvage yard with lots of shiny new parts. The idea that you must always buy expensive new factory parts just accelerates the date of their economic obsolesence.

I agree, in other words, they are white elephants, or will be at some point. The local MB dealer just sold a 1995 S320 for $7995 and a 94 E300 for $2995. Do you think the new owners are going to spend thousands of dollars a year on oem repairs? I doubt it.