June 2003: Wiring Harness Restoration & More...


There is no end to the messes you will find in some cars. This is my wiring harness, 28 some years old and the worse for wear. I think there was about $11 worth of Midwest real estate attached to this baby, and some corrosion in the wrong places. Well, this is the root of many '02 evils... namely grounding problems.  Look at the bright side - this thing wasn't made by Lucas!

Facts about 2002s - the wiring harnesses are different, in some case every consecutive year was a change. Seat belt buzzers or not, electronic fuel pump/not, square vs round tail light/not... There is probably no chance in hell BMW Mobile Tradition will ever rebuild these things - if they did they would be a zillion dollars as there is not much call (unlike British cars with Lucas built harnesses) to gut the wiring harness. So as the story goes, you have to just get in there and do the things you do everywhere else. In my case, I started by removing all the relays and soaking the entire mess in a 5 gallon bucket of hot soapy (DAWN) water for about 2 hours.  How could it be any worse off than it is, right?

Before I get started, I have to give all the credit of a great wiring wrap job to my wife Mary. Her expertise in carefully and patiently wrapping the tape for the job really shows in the photos of the completed work.
 

When you start unraveling the original friction tape used on the harness, this is what you find.
In certain sections, the factory used electrical tape to hold the bunches together. Here is a before/after shot showing new friction tape. Quite a difference from the "old muddy" look.
Ok here you see the harness after the hot soapy water soaking. There are just a bunch of these places where the wire is openly visible with 3/8" friction tape. This width of tape doesn't seem to be around anywhere. You have three options, wrap it up without the space or cut a roll in half to use.  I chose the third route... (more later)
Here is the most common tapes available from 3M. Even places like WalMart carry this stuff, so choose your weapons carefully, cost is an issue because you will need about 8-10 rolls of either for the whole thing. Don't forget to use the LECTRA CLEAN to remove engine grease and tape slime. I also used liberal amounts of Wurth's Contact OL Solvent on all the contact areas to dispel corrosion (LINK TO BUY IT HERE) on the whole harness.
OK, here's where I deviated from the norm:  After wrestling with the nasty friction tape I found out how easy it is to get dirty. I figured the first time I get near a dusty road it is brown again. So I choose to go the hi-temp electrical tape route. This will help in strength, size and looks. The harness with all that friction tape is one of the primary reasons the harness is so hard to deal with in the first place.  So I've chosen not to be original in this area for purposes of longevity. Hey, nobody likes dealing with electrical problems so I'll take the heat on the cosmetic differences later.  I'll also use liberal amounts of heat shrink tubing where necessary to prevent Mother Nature and engine solvents from invading the wiring again.
All of your inside wiring looks like this with the spacing. I chose to cut down some of the electrical tape to make it look like the factory did it in the bigger areas, and used a white fiberglass tape for the smaller areas.
Here is another view of the area that is behind the firewall. The important connectors such as grounds are to be cut off and replaced with new ends that will ensure proper grounding.
A reminder here this is something that takes a lot of patience. I worked on about 6-8' per night until it's completed. I still have common spade type ends of the wire to go before it's all done.
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