I just replaced the engine wire harness on my newly purchased 1993 300SD. It took about 45 minutes and part
under $300. I did it because it was starting to fall apart. Outside plastic spiral loom cover almost completely gone, and wire insulation missing about 20% of wire. Eventual will cause a short. In emergency or
if cannot find new harness could seal with spray on coating of some kind- rubberized or varnish type. Much easier to replace. Anyway my question is- what about the other wiring harnesses??. They seem intact -especially the harness away from the heat - to transmission etc. but I don't know for sure and would have to tear or cut off plastic wraps or covers to exam wires and didn't want to do that. Do the rest of the harness degrade after time. I just sold my 1983 300d and wiring harnesses perfect. Also my 1986 300sdl wire harness are fine. What do I have to look forward to in my 1993 300SD diesel. I keep my cars sometimes for 10 years . Any experiences with wiring harness - please let me know. [?]
As I understand, this insulation material was used from 1992 to 1995.
Someone has recently posted that it is only very late 1992 cars that have the biodegradable insulation. At any rate, from my experience following this forum for the last 1.5 years, nearly all problems are with engine compartment harnesses, which are subject to extremes of heat. I seem to recall that someone may have had a problem with an ABS sensor wiring harness (or it may have just been the sensor itself).
It's a good idea to spot check the other harnesses just for good measure. Peel open just a couple inches of wiring and have a look. No "damage" that a little electrical tape can't fix.
The wiring harness on a S420 with a V8, is that a DIY job, considering the I6 took only 45 minutes? What problems can arise from a deteriorating wire harness? Thanks in advance.
Really not familiar with gas v8 . Probably more involved. Actually by the time I put nylon wraps took closer to 1 hour. Anyway here are some general instructions.
1. Check route of wire and see that it will pass thru all openings(between manifolds etc.) You may be able to leave old wiring in place temporily.
2. Diesel had 8 connectors + ground + main connection.
Place new cable parellel to old and start unplugging and plugging in new one. Be careful with removing old - some connectors have clips and you may need a little prying to remove(move the clips etc.) There is a round plug on diesel that you must leave inserted and rotate a small plastic arm to unlock the plug otherwise will not come out.(this was a triple recepticle plug)
3. Take your time and don't get frustrated- all the plugs will remove fairly easy(unless you are not pressing on little plastic releases etc.(examine new ones to understand how they disconnect.
4.Get a good light and examine old prior to removing
to see how wires are routed- you may not have room to leave old cable in everyplace(I did). If not label anything you might get confused on.
5. After you complete job - use nylon wraps to secure
cable. Keep harness away from touching hot spots etc.
6. Your are finished - Buy yourself a beer and celebrate. I saved at least $400 from a non dealer job(independent mechanic) and maybe 700/800 from authorized dealer job. Plus all that satisfaction that you can fix your car yourself. [:)]
Thanks guys. We went from one extreme (6 cylinder) to the other (V12). My harness is not so bad, but I'll need to change it sooner or later. PCMAHER, you have a good website. In a month I can add stuff to it or to the knowledge base if you wish.
Some things I have done are spark plug change, fuel filter change, air filter change, oil/filter change, coolant change and checking/adding R134a Refrigerant. Give me 3-4 weeks until I move, and then I'll get the information to you guys. Promise.
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