Many thanks for the update with the solution, this will help others. Did you also determine how the leaves/needles were able to get inside and prevent this from happening again?

Regarding the HVAC and radio lights not working....does the dimmer control work for the other lights?

 

I am confused about 1./ what resistor and 2./ what airbox cover and 3./ which coil? you are talking about on your 1998 Blazer. Could you please explain?

 

My floorboard is still getting wet when running the AC. I have a good steady drip out of the airbox when I'm sitting still. My baffle is gone-the foil/paper insulation cover turned to dust long ago. All I can figure is when I'm driving down the highway the condensate is getting blown back onto the firewall and getting in somewhere. It's always the very bottom of the floorboard, never wet where the floor slopes up to the firewall. Any ideas what could be happening? I've been dealing with it by removing the floor mat and letting it dry before mold can start.

 

After a long struggle with this problem I FINALLY found the culprit. While putting up my tools in the rear cargo area one day I felt the carpet was wet around one of the divots for the cargo hook. After pulling the bottom trim and lifting the carpet I found the entire rear area was wet and reeked of washer fluid. The trouble was the washer fluid line where it connects to the 90 that runs up to the rear window was split. I had my wife hit the rear washer button and it sprayed everywhere inside the protective black strip. When not in use washer fluid was siphoning out constantly, which explained why my reservoir always seemed to empty out much faster than it should have. The fluid apparently ran out so much that it was running down off the cargo area 'hump' and traveled the floorboard where it would gather on the passenger side. After cutting out the broken part and splicing in some new washer line the floorboard has remained dry. Hopefully this helps others by looking in a spot they would never guess could cause the problem!

 

That's kinda crazy the washer fluid was leaking that much! Thanks for sharing what you found on the source and solution.

 

Haha ain't it though! I told myself it was condensate but in the back of my head was a voice saying it didn't smell like stale water or antifreeze and it never molded or mildewed. As for it siphoning out I would think the pump wouldn't allow it-but it is an el cheapo pump from O'Reilly's as the OEM didn't work when I bought the truck. (Maybe a PO placed something heavy in just the wrong spot to break the line.) The reservoir is higher than the line that broke and with the end being pretty much open due to the break it allowed the siphoning to happen.