Warm AIR comes out WHEN AC UNIT is on i just

Are you noticing if your AC compressor is coming on? When you have your car at idle, toggle the a/c switch from the off position to the on position and pay close attention to see if there's a drop in RPM's when you toggle the a/c switch to the on position. If there is, the compressor is being activated in which case, the warm is not being caused by that, but if the a/c compressor is not coming on (and I suspect that's your problem) you are going to blow nothing but warm to hot air. Thanks!

Check that the heater is turning off as the hot air will over come the cool air. Check that the clutch on the a/c pulley is still engaging as it the unit was over filled or has a leak from a badly fitted pipe the high low switch will not allow the compressor to work.. If the work was done professionally check that the correct gas was used and seek warranty for the problem.

Is the radiator fan still coming on ? Is the compressor running ?

see if the cooling fan turns on when the ac is turned on if not the pressure builds to high and shuts the compressor off

The AC compressor will come on when you turn on the defroster. If you're not getting heat it's most likely that your heater core is going bad. You can flush it out and see if it's getting clogged. Also check your water pump to make sure you have enough flow through the core. The reasoning behind the ac blowing when the defroster is on is that it blows dryer air on the windshield.

Cooling fans working? If you notice the air getting warm mostly while stopped, probaby cooling fans not turning on. if the fans are working properly, may be low on freon and need a recharge.

there is a clutch under the pully you see turning that allows the belt to turn without running the compressor.you may want to check the optimum pressure rating for yuor truck.it sounds to low to me.check that with your local auto parts dealer.hope this helped

you need to have it diagnosed by a professional. These are complicated systems even to a trained tech. You may be over or under charged, have a clogged expansion valve, have a leak or many other issues. This model has a rcv refrigerant control valve inside the compressor which regulates the pressure of the compressor. If you notice the compressor never shuts off like conventional auto a/c's do the only time the clutch works is when you turn it on or off. Can be complicated.

Most likley needs to be recharged. Shouldnt be low, but if it has ever been in an accident it may have a leak or your mechanic stole the refridgerant when it was cold outside and you didnt notice untill you turned the ac on.

If your refrigerant level is OK and the truck blows cold air your compressor should be fine, in which case the noise is probably coming from the AC clutch which isn't too expensive or difficult to replace. If it doesn't blow cold air, switch the AC on and watch the compressor. If the clutch engages, but the compressor doesn't turn, the drive belt will squeal loudly and probably start to smoke. In that case it is the compressor which is expensive to replace. Most vehicles have an AC bypass that will temporarily cut out the compressor clutch under heavy load. If you are going uphill with the AC on or accelerating heavily you might notice warm air coming out of the vents for a short period until you let off the gas.