Possesed Car

#1

Dear Car Talk,



Myself and others are experiencing difficulty determining the cause of my cars problems; it is an automatic 1989 chevy caprice that has electronic locks that have worked fine for years until a few months ago, the passenger lock stopped operating. The driver side lock still worked as it was supposed to so i didn’t pay much attention to it until a few days ago when i was driving and a spark lite underneath the driver side steering wheel. The windshield whipers quit working mid motion and the doors started locking individually (mainly front if not only front)even when the car was not running. 16 hrs passed and I found my battery drained and the doors were no longer locking. I charged the battery and the doors continued locking individually so I let the car run for an hour to recharge the battery. This time about 8 hours had lapsed and the car once again had a drained battery and the doors stopped locking by themselves. Has this happened to you or can you tell me how I should proceed?

#2

You have a short circuit. Maybe more than one. The spark was a bare wire making contact with metal somewhere under the dashboard.

A fuse should have blown when the short occurred. That may be why the wipers stopped working.

The automatic door locks are draining the battery, and will continue to do so until you can stop them from operating.

I would start inspecting fuses, and would pull the fuse from the door lock circuit, or remove the relay, to stop the locks. Check the owner’s manual for a list of fuses, or look at the fuse box cover. Sometimes there is a fuse diagram on top of or under the cover.

There are fuses and relays under the hood and inside the car. Check them all.

You have to find and correct the short circuit before you start replacing blown fuses. A short circuit can start a fire in the car, and that could ruin your whole day.

#3

While I wholeheartedly agree with McP’s diagnosis, you may want to consider whether you’ve gotten your money’s worth out of this car. Multiple shorts to ground from chafed wiring harnesses can be a sign that the 19 year old insulation is going to be prone to do this again, and wiring harness problems can be horrible to trace down.

The door ones wouldn;t bother me so much, as the wires often on old cars chafe where the harness goes through the pathways between the doors and body, but the one under the dash would leave me wondering. Even insulation gets old.