headlights 968

[rhill5371]

:help: Any ideas on troubleshooting my headlight problem. I have a 1992 968 and when I try to turn off the headlights they won't go down. I have to screw them down manually.They are individually powered'not like the 944.Also they will go up when I power them back on , but won' t got down. Help :help:

[artysan]

I have had this happen on my 1993 968 Coupe. It is a transistor inside the headlight controller module, which actually looks just like a relay but has many more pins. This module contains 4 relays and the transistor/diode logic that work with the mechanical sensors and motors in the headlight assemblies. I can't imagine very many people have the electronics background to actually replace the single surface mount transistor that fails, but it is for some reason always the 'lowering' transistor that fails.

I did the fix and everything was fine for quite a while, but the problem has returned. I also have noticed that a trim ring in my passenger side headlight has broken off its mooring and suspect it may be physically constraining the lowering and causing the transistor to overload and blow, so I plan to fix the headlight first, then replace the transistor again. I have included two diagrams for you. One is a physical layout of the controller circuit board and pinout of the module for troubleshooting. The other is an actual schematic of the controller. The transistor which fails is a PNP type. I used a 2N3906, a very common part, and carefully retrofitted this non-surface-mount component to the surface mount circuit board. It also commonly burns out a couple of resistors in the chain as it takes a bit of current to blow this part.

If these instructions are more technical than you are comfortable with, they should be detailed enough for any electronic bench tech to do the repair for you. Check for mechanical issues first though.

968 headlight CU.pdf

968 headlight CU 2.pdf