After a day of wheelin, the AC/heater fan doesn't work on positions 1 and 2. But it still works on positions 3 and 4. Weird huh? Any ideas?

 

Likely the #1 and #2 speed resistor coils are burned out on the blower motor resistor, easy repair:
- http://www.4crawler.com/4x4/CheapTri...BlowerResistor

 

thanks for the help. I've also noticed that both my passenger side reverse light and my passenger side brakelights have blown. Both work after replacing the bulb though. What could all this have been caused by? Like I mentioned above, this was all after a day of wheeling, which included the use of an air compressor hooked up to the truck battery. I'm guessing it may have had something to do with the compressor. But I'm relatively clueless. any thoughts??

 

Micro Electrical Storm? Or, the Perfect Storm of 22 yr old bulb filaments subjected to 12 hours of vibration and jolts, accompanied by a series of voltage/current surges? No mystery to me.

4Crawler is giving you the good dope on the blower motor resistor pack! The "AC fan" is the blower fan.