Posted by Patrick C88 750 some years ago on BB: Arcing (from the inductance of wiring to the Reverse Lights) and Amperage (3 Amps) heats up and gradually degrades the contacts in the gear shifter. I added a relay near the shifter so now current through the contact is reduced to 0.1 Amp or so and not much energy to create an arc. Hope that cleaning the shifter contacts is a thing of the past. First, remove the shifter handle and lift open the wood cover. I cut the BLU/YEL wire to the plug Pin-7. Plug side wire went to the relay, control High side. The control Low side was wired to a ground which is a mounting bolt of the shifter assembly. The other BLU/YEL end went to the output of relay. Plug Pin 6 is the voltage input to the shifter. I spliced the GRN/BLK wire and exposed 3mm of copper, then solder another wire from that point to Relay Output High side. Pretty straight forward. No need to remove battery; just remove key from ignition switch. Check that the Reverse Light turns on when shifter moved to the R position and does not turn on at any other positions and that's it. Wrap the relay with some cushion to prevent it from rattling under the center console. http://www.bimmerboard.com/members/c...ding_Relay.jpg
Forgot to take a photo before I wrapped up the relay. Anyway I used K-spec Female crimp terminal like the one in the photo insert. http://www.bimmerboard.com/members/c...elay_photo.jpg

Photo of which Plug and which wires to modify: If you already lost Reverse lights or lost the display of letter "R" on the dash then you'll have to remove and open the actual arc-shape shifter to clean the contacts. Otherwise, if shifting has been normal, then just pull out the 8-conductor black plastic plug and do the cutting, splicing and soldering, etc to add the relay. I just used an old relay dated 1987 left behind after I replaced the main relays. http://www.bimmerboard.com/members/c...lay_Before.jpg

Q&A:
How do I get to/Where do I find that contact? My reverse lights still work but I believe in preventative measures and want a back up. I was at the local pick and pull on Friday ('78 Ranchero for the picking - I need a new bumper), and I spied an early 750il relatively unmolested. I plan to go back this week and do some gleaning....George E32 750il 03/91

the contact is on the shifter/range switch. lift up the cover around the shifter lever and you will see the switch bolted to the bottom of the shifter. on my car I can pop out the (auto-manual) switch next to the shifter lever and stick my fingers in to (carefully) lift/wiggle the cover up and off (remove handle first at the top). 750IL 1990 (9/89) Black,

Not every one has fingers like toothpicks and a grip like an ape. Give us old guys with stubs like a 1 inch pipe an easy way to get at this thing. I used a set of small flat blade screwdrivers like chopsticks to wiggle it out. 03/91 750i

That probably explains why I have no reverse lamps on my 750 anymore.

yup, yours probably looking like these: I done 4 of these among different cars now. http://www.bimmerboard.com/members/r...iginal/ss1.jpg http://www.bimmerboard.com/members/r...iginal/ss2.jpg
http://www.bimmerboard.com/members/r...iginal/ss3.jpg rv8flyboy 750IL 1990

so do I need a working selector switch in the console before I can do this modification?

Short answer is yes, the contact needs to work to activate the relay. sometimes you can clean the switch unit and get away with it to activate the relay. http://www.nmia.com/~dgnrg/page_13.htm
http://web.archive.org/web/200812292.../e34a/id4.html

Thanks for adding the brief, but concise writeup & pics. Very purposeful. I now have a new upgrade to add to the to-do list, as I noticed both 7's had burnt contacts in this circuit when I cleaned them.
Cheers! Cars: 05/91 735i, 236k km's; 03/94 750iL 238k km's;