I have a 2007 Trailblazer. The lights on - key in ignition alarm, only works when there has been a week or so of low humidity and high temperatures. The radio sound on same speaker also does the same. As soon as it rains or humidity is high, it quits working.
Also the drivers door will lock itself when the key is in the ignition, even when it is running.
All I get from the dealer is it will cost $400 to do a test. Is there anything that I can do myself to find the problem?

 

All I can offer is to check the wiring in the loom that goes from the door to the car body. With all the movement those wires can break and short out. When my power windows stopped working, I found a broken wire there. It took a while too since both wires were buried and had nearly been pulled out of the accessible area.