This morning, not an overly cold morning but I had a thin layer of frost on the windsheild. I started the truck and she turned over without a problem.... Typical morning.

But, then I turned the heater on and to defrost. I waited and waited and it never went to defrost. I got in it and started driving down the road and pulled over into a stop and rob gas station about a mile or so from the house and it still did not turn to defrost.

No gauge problems, no codes, all okay; so I proceeded on my 30 mile treck to work. Finally, the defrost worked as the engine heated up and I could change the defrost back to front air, foot air, etc, with ease.

Is there something going out? Compressor, switch panel, etc? I have never had this problem before, that I have noticed at least. It has only been the second time to run the defrost this season, would that have something to do with it?

 

There was a TSB about this before. One of the little doors under the dash malfunctions and won't close. Mine does it and I was too lazy to get it fixed while still under warranty. Now I have to live with it. I just turn it to AC and back to defrost a couple of times and then it will start working. Once winter hits, I always keep it on Defrost.....
http://dodgeram.info/tsb/2003/24-004-03.htm

 

Actually the TSB concerns the fact that you will not get floor heat. The other fuctions will normally work fine.