Auto Parts: door lock relay 1991 chevy truck 1500, ground terminals, chevy truck

Question
 Where is it located? the doors will lock,but not unlock.

Answer
Hi Charles,

the door lock mechanism is integrated with a ground-float relay which means you cannot change it individual of the unit. the door lock mechanism is located inside the door. There is a master relay located in the fuse/relay center but if it were bad, you'd have NO power to the locks so we can rule that out.

There is a very good chance that only ONE lock mechanism has broken. This affects ALL the door locks. You need to test each one to find out which one is bad. If all test ok, then the next step is to check the wiring for a break.

I have run into issues similar to yours and to test the ground in the door I've attached a second ground from the chassis of the vehicle to the metal part of the door. If this fixes your problem, replace the ground terminals (it's a 'float' so there are at least two ground terminals in the door harness and you may have to ground ALL the doors that use locks). Having a bad or faulty ground-float typically causes the windows to work erratically also, like slower in one direction than the other or periodically not working at all so if you are experiencing issues like that, a ground is more likely than not going to be your fix.

You may also want to test the operation of the switches as this may be another cause of bad contact.

Thanks for the question, I hope this information helps you.
KB