I know that the AC cycles on and off when in defrost mode, but why does it also cycle on and off (like defrost mode) when on floor and vent mode? It doesn't cycle when on floor only or vent only?!

 

Mine does the same thing. Drives me nuts. It's not set on AC but the AC is cycling on and off. Vent or floor no AC but Vent and Floor mode AC is on

 

same here. Its ridiculous

 

haha, ridiculous!

mine does it too, sorry i can't answer your question though. hopefully someone can.

 

When I first got my truck, I brought it back to the dealer for just that. After much digging, the service manager said that it's supposed to do that, even though the dash control doesn't have the little 'snowflake' next to that position.

 

Thats just the way it is. Look in your owners manual.

 

i must not have ever used that position.

 

My 98 has the snowflake next to that position. But my freinds 99 dose not, and dose the same thing.

 

It turns on because A/C blows DRY air. That's what you need when your windshield is fogged up. Next time you're in a different car and the windshield fogs, try to de-fog it with the A/C off, then with the A/C on. You'll notice with the A/C on it'll de-fog much much quicker.

 

It will also cycle the AC to keep the fitting seals and compressor seals lubricated in the cooler months.

 

The "problem" is pretty easy to overcome by installing a switch to turn the A/C off and on whenever you want.
Instructions> http://dodgeram.org/tech/repair/HVAC/Defrost_AC.htm