It's an odd mix of what sounds like 'electrical gremlns'...
I only say this because I had all kinds of weird things happening on my 89 that were seemingly unrelated!
Fixed a couple bad splices in the harness on the driver's side and then went around and CLEANED the ground bolts and surfaces with steel wool and put them all back on. (Took about 1 hour) This has 'fixed' 6-7 things that seemed totally unrelated on the car.
It fixed a low idle problem, the keyless entry, two of the courtesy lights, the 'Check Gage light' , my oil pressure gage, both rear panel speakers and my cars ability to blow out $40 turn signal modules.
Now looking at the wiring diagram you wouldn't think all these things would be related...... But fixing as many splices and cleaning all the grounds on the car seems to have fixed all these things. (fingers and toes are crossed....)
It's worth a check!
Lance