I posted a thread many months ago about my recently acquired 1985 500 SEL. Originally, I bought it with a bad engine and installed a 3.8 which was recently rebuilt in it. The fuel relay switch had to be replaced twice because of idling problems but the big mystery is the car runs fine until I turn the headlights on - then it dies immediately. I tried unhooking all headlights and turn signals under the hood but then the car wouldn't even start. I did not get any replies to my original post and the car has been in the shop for other things for a while. Any suggestions now would be appreciated.

 

Does it have a Factory Alarm? If so this is where I would start due to the fact that this is the only electerial that links the two.

 

Yes - it does have an alarm. It does not have a sound but if the dorrs are not unlocked by the key, the lights will flash and it will not start. If you can tell me where the alram is located, I can try to disable it and see if that fixes it unless you have a different suggestion. thanks

 

The alarm system on this car is very complicated. It is activated by a switch on the drivers side door handle and also through the factory radio. Does it still have the factory radio? If not this is where I would start. If it does try to locate the alarm brain and disconnect it. This should eliminate the alarm system.