My blower was going out. worked fine most of the time, but often would not work at all, so I purchased a replacement at the local auto store. I researched the forums and found it was suggested to replace the resistor as well for good measure, since one can make the other go bad, so I replaced that,too.
I parked the truck after work, got up the next morning to a totally dead truck. I hooked up my little booster pack, which was way too small to start the truck, but I discovered the blower was on, even with key off. Since the motor ran all night, i figured that was what caused the current draw. When I shut the truck down, the fan stays on, but if I move the heater selector to "off" it turns off. I thought I was safe for the night, but the battery was dead this morning as well.
An other new mystery. The radio now has gone crazy. It has power (clock works, can see the station it's set on) but no sound to the speakers most of the time, but then sometimes it works fine. When I was just parking at work, I discovered I had sound in Park and Neutral, but not in Drive,2 or 3,
When I shut the truck off, with key off, I still hear clicks, as if a relay is still operating, When I switch through the heater settings, I hear the same (or similar) relay click with key off.
Sorry for the long post, This has really got me stumped and it's my only vehicle. If anyone has an idea how to troubleshoot this I would really appreciate it. Thanks!

 

do some searches on water leaks from windshield seal, the water can cause simalar symptoms,otherwise bump to the top

 

The wiring in the steering column can chafe and short. This is a suspect as well.

 

This sounds like a steering column issue since the gear selector affects the problem/symptoms.

 

This was one of the most bizarre things that has happened in the 12 years I've owned my truck. I did the blower motor change-out in the rain, something must have gotten wet somewhere to cause this, after 3 days of drying out things seem to returning to normal. Truck started this morning and the radio has stopped having a mind of its own. Thanks for the help, I'll let you know if things change.

 

This sounds like the good old windshield leak, water leaks into the interior fuse panel and makes everything go nuts. Get the windshield re-sealed and if the symptoms persist replace the interior fuse panel.