Headlights and Daylight Running Lights All Go Out Intermittently

[RatherRideMyHarley]

Late Friday night my car was parked on a fairly steep street at a friend's house. My headlights wouldn't come on when I went to leave. The parking lights did. I switched back and forth between the Auto headlights and daylight running lights and they were all out. I decided I could see well enough from the amber glow of the parking lights to go the 2 1/2 miles home at 1:15 in the morning. When I made a sharp u-turn to the left in an intersection a 100 feet from where I was parked and started heading up hill my lights came on. They worked all the way home. When I made a sharp u-turn to the right at my driveway to reach the mailbox without getting out of my car they went out again. They stayed out when I made a second u-turn to the right to head back to the driveway. When my front tires hit the driveway apron they came on. When my back tires hit the apron they went out again. I could not get them to come back on in the driveway or garage. I have a relatively long driveway. I'm the original owner and I've had the car for a little over 21 years. I've never had a problem with the lights before except for some burned out bulbs and getting water in one of my headlights due to my faulty closing of the headlight compartment once.

Researching Saturday morning it seems like it could be the LCM (Light Control Module) which appears to cost a little over $600 USD for the part and another $400+ for the installation and programming. The part replacement is a 5 minute job but the unit has to be programmed. I'm sure my stealership will charge me over $1,000 to replace the LCM. I would like to look at the wiring harness and see if the wires have been rubbed bare or chewed bare. I get mice in my garage and Z4 occasionally. They're no friend of mine! There seemed to be a correlation between sudden car change of direction and the lights going on and off but that could have affected either the LCM or the wiring harness. There's no obvious reason for them going dead while the car was parked. I drove it down hill at the same slope to park there and they were working as they had for the last 21 years.

I can't seem to find a wiring diagram. Does anyone know where I can get one or better yet advise me where to look at the wiring harness? I'd like to inspect the wiring before either taking it the BMW dealer, my independent European car service shop or replacing it myself. I will probably go the DIY route if I can establish that I can program it with the code reader I have. I've never used and don't really know it's capabilities. The reason I bought it a few years ago self resolved before I tried to use it.

 

[buzyg]

That sounds like you could have a loose wire earthing somewhere. Once you get a wiring diagram take out the related fuses one at a time and see what changes. Will take a while. Good luck.

 

[RatherRideMyHarley]

I seem to have found a couple of wiring diagrams. The lights all have their own electrical supply conductors of various colors and brown conductors to ground. The only way 4 or 6 light assemblies (I can't recall if I tried the fog lights when the other lights were out) could lose and regain their power simultaneously because of a loose or damaged wire is if at some point or beyond all their ground wires are assembled into a common ground wire. Does anyone know were that occurs if it actually does. It does make sense to have one larger wire going to ground vs several and then dozens of small wires all traveling to ground.