How do you troubleshoot a trunk lock on a 1992 Buick Park Avenue?

Answer 1

Buick should be sued over this one. They admit in their manual that this trunk feature can easily break and they admit that it can kill you, yet they go ahead and implement it with just a warning in the manual that most people don't read.

For whatever reason, the relay switch on the trunk motor can easily fail. I suppose it depends on what position the latch is in when it fails as to how serious the problem. I bought my Park Avenue used the other night knowing it had this problem and that I could solve it. Before I give the solution, here is what my local Buick dealer said "it's probably a bad motor and they cost hundreds of dollars".

As I was removing the grey trunk liner from around the motor I touched the lever on the relay and the motor turned and latch went down. I closed the trunk and opened it again and the latch came up but I could never get it to go down again. So, I unplugged the wires going into the relay. I got a star driver and removed the screw that holds the relay to the motor and latch gear casing. That exposes two metal tabs that lead to the motor. I got a 9-volt battery (I keep them around for my smoke alarms) and two wires that I have with alligator clips on each end. I clipped the two wires to the motor leads and left the wires to hang out of the trunk then closed the trunk. I clipped one wire to the negative post of the battery and then touched the other wire to the positive. Nothing happened (visibly, but the motor was trying to push the latch up. it was already up). Then I switched the wire from the negative post to the positive post and touched the other wire to the negative. The latch lowered. If you make it go too low it won't easily close without slamming, but this method makes it easy to position the latch exactly where it needs to be. Then just pop the trunk and remove the wires. I left the relay switch off and the trunk now operates like a normal trunk.

The latch has two tabs that flip a toggle switch as it raises and lowers. If you have the "trunk ajar" light lit and it won't go out (I either don't have one or it's burned out) then you should be able to plug the harness back into the relay but don't attach the relay to the motor. Just flip the switch down and the light will stay off.