1979 Pontiac Trans Am-Test for GM dome light courtesy door switch failure, part one
In your older GM car, are your courtesy lights stuck on? auto appraiser Jason Phillips notes that most GM button switches located in the door jambs, used to break ground to the circuit operate the same way. The switches are threaded into the cowl jamb post, and are spring loaded. Often, the left switch is a two wire, one side to the courtesy lights, and one to the ignition buzzer. Both are supposed to be hot leads, so do not be confused, thinking that pushing in the switch will cut power to the other side of that switch. Most switches on the passenger side are only a one wire connection. You can un-screw the switch and pull the wire spade connector right through the hole on either side. You don’t normally need to remove the kick panel to remove the switch. Pull them out, un-plug them and test switch for continuity. Use an electric wire wheel to clean them up while their out, freeing them of decay and possibly old repaint build up. Where the wire spade connectors are now hanging out of the holes: if you have 12 volts at all three spades, and both switches check out for continuity by breaking the circuit when they are pushed in, then you should rule out those items as the source of stuck on or off dome light problem. The follow up diagnosis is posted later in this blog.
Tags: Classic car chat, Pontiac, Techinical