In Reply to: Re: update on LKM for early 90's V12's posted by Max Fretter (NZ, 87 735i) on April 04, 2001 at 03:09:34:
I thought you were taking a vacation! Yes, the resistive elements are for current sensing. The LKM has differential amplifiers across each element. These amplifiers sense a very small voltage drop across the metal and compare it to a known value. If the difference is too great (e.g. bulb is out), an alarm signal is sent to the OBC.
As far as I can tell the metal resistive elements are series resistances for current sensing, probably for failed bulb detection...
Just thought I'd share some knowledge I'm collecting about the LKM (Light Kontrol Module) in early 90's 750's. Unlike many late 80's LKMs, the early 90's LKM has only 3 relays. There is an empty spot on the PC board but no relay is installed. The relays are associated with three light groups on the car. With the LKM installed in the fuse box, and looking down on it, the relay toward the front of the vehicle is used to turn the low beams on. The one right next to that relay is used to turn the high beams on and the one closest to the driver is used to turn the fog lamps on. The two contacts on each relay are in parallel (two single pole single throw contacts on each relay) for reliability and the relays pull in when the lights are turned on. I have not yet been able to discern the relationship between each of the metal resistive elements yet, but that understanding may come shortly.