I brought my truck in to the dealership for some AC work. The AC was blowing hot air, this is the second time. The first time they said there was nothing wrong but recharged the system?. It did'nt make sense to me but the truck is still under warranty. This time the front seal on the compressor was bad, changed and recharged the system. The Ac blows cold when you first start off then gets warmer the more you drive it. The compressor does not kick on. The settings on the truck is max AC and recirculate on. I brought it back and the tech looked at and said since it was so cold out the compressor would not come on. Yesterday it was below freezing all day. When we brought the truck in the shop it worked fine. He drove it and said that when it gets this cold the compressor will not come on, and since the truck was in the shop it was warmer and the compressor would come on.

 

They told me to bring it back when it warms up if there is anymore problems. My question is can this be true?. I have never heard of this before, to cold for the compressor to come on. Sorry for the long post.

 

I think they're wrong bud. When you turn on the defrost, the compressor cycles. It should not get warmer the longer the truck is driven.

 

I don't know about my truck but my VW would not let the A/C compressor run if it was below 45 degrees F outside.

 

Sounds like the evaporator is freezing up, which is normal if it's not hot outside. The suction and discharge pressures will be low enough that the compressor may stay off/cycle rapidly to try to keep the system from freezing up - operative phrase being "try to." Under those conditions, it won't take much for the evaporator to freeze.

I'm kinda curious though, why in the hell are you running your A/C if it's below freezing?

 

I think below 40 degrees the compressor does not come on, even in defrost mode. I remember reading that in a tech manual or owners manual sometime back. If it starts off blowing cold and gradually gets warmer, thats sounds like a problem to me. Could be a freon leak, bad compressor, or vacume leak.

 

While your system may need further service (wait until it's warmer to find out), the tech was generally correct regarding low temperature operation.

The static pressure in the system can drop enough at very low temps (due to the contraction of volume of the the refrigerant) that the resulting pressure is not high enough to trip the pressure switch (45 psi). There is no "sensor" in the system that detects low ambient temps and disables the system. This behavior is simply a byproduct of thermodynamics.

Steve

 

First, the reason I was turning on my AC is that on sunday it was 80 degrees before the cold front hit, My app. at the dealership was on tuesday. I will wait to see what happens when it warms up. Good thing is that my warranty is about up but the service writer said since this is the second time about the AC they will cover it even if the truck is out of warranty.