Instrument Panel light fuse blows

[PHLambert]

1995 K1500 LT 3.5L Auto 170,000 miles

This has been an extremely reliable truck, albeit with a few annoyances over the 10 years I've owned it. The motivator for this message is the instrumental panel fuse blowing, but I thought I would dump the whole list of current problems in here, just in case they are related somehow:

While driving last night, the instrument panel lights went off (and the clock illumination went to the bright mode). A pop was heard, and when I got a chance to stop, found the 20A fuse blown. Replaced the fuse and the lights worked again. This morning on the way to work, again the pop and they were out. We've had torrential rains for days here, and the truck has been outside all day in most of it.

In the past couple of weeks, I've notice that the air from the rear heater has gone from hot to warm, and now is only cool (probably the temp of air at the intake in the back).

Whenever it gets really cold, the interior lights come on when I first start the truck if it's been sitting outside, and the door open alert sounds. As the truck warms up, the alarm will go off, then after a while, the lights. A small tug on the driver door shuts off the alarm and lights. I've duct-taped a nickel to the pad on the door where the driver door switch actuator hits, and this problem goes away. The GM dealer says these door switches are a pain to replace, and most people just duct tape the actuator. At least my way the interior lights still work.

The front heater fan sounds like something is caught in it. It gets worse when it's cold. Doubt that this is related, but thought I'd throw it in.

One more unrelated item: when the a/c clutch pulls down, the a/c compressor makes a sound reminiscent of when I used to clothespin a playing card in the spokes of my bike as a kid. The GM dealer says it's working fine, and no need to repair/replace. But the noise is loud, and a little embarrasing. I'm about to take a 2,000 mile trip with it, and hope it doesn't seize and snap the serpentine in the middle of nowhere.

Thanks for your advice.
PL