Hi all.

The central locking system in my '90 740 T Wagon is not working. The key unlocks and locks the driver's door, but no other doors including the tailgate are triggered.

Coincidental to this problem, I cannot unlock the tailgate from the outside with the key. I can open the tailgate from inside the car, but the key won't do it. Once I close the tailgate, it's locked. What a pain in the neck.

I'm not sure what's going on here. Might the tailgate lock be broken, and subsequently screwing up the central system? Or is the central system messing with the tailgate lock? Or are the two urelated? I cannot swear that the two broke simultaneously (it's my wife's car), but it's very possible they did.

I don't suspect the fuse or the relay. The fuse appears to be okay. I pulled the central locking relay, popped off the cap off and the movable contacts appear to be free and not seized. The relay is shared, oddly enough, with the low beam head lights, and sure enough, the lights work fine, and when I removed the relay, they ceased to work until I replaced it, when again, they worked fine.

Any thoughts? Anyway I can check things electrically? At the driver's door switch? At the tailgate? I have a multi meter (but no idea how to use it).

Tomorrow is supposed to be fairly warm, and I'd like to try to fix it then.

Thanks,
m rad