I have a 2002 GMC Envoy , A/C blows cold and then sometimes it just starts to blow hot.?

Answer 1

Probably just need to be topped off.

Possibly the air conditioner clutch too.

Answer 2

I would check the pressure of the R134a (freon) while it's running and blowing cold. It should be between 35 - 45 psi on the low side. You can do this yourself with an inexpensive a/c guage from the store, or have a shop check it. If that's good, I would start cleaning and checking the electrical connections to the magnetic clutch on the compressor and the switch on the drier cannister (large aluminum cylinder, probably located on the right/passenger side of the engine bay by the firewall).
Another possibility, odd as it may seem, is that the air ducting has a problem that causes it to run air through the a/c, and then the heater - especially if you have electronic temperature control. If this is the case, I would suggest taking it to the dealer or a qualified repair shop.

Answer 3

Since it blows cold sometimes then the system still has freon in it or it would not work at all due to a low pressure switch. This in mind, if the vehicles compressor relay sticks on it will cause the system to freeze externally and will not allow it to blow cold air in the vehicle. If you let it sit or turn it off for a few minutes and turn it back on and it blows cold then you know you need to replace the relay.

Answer 4

lots of opportunities. it must be the radiator fan is coming near irregularly because of the fact of a foul thermal sensor, the thermostat must be sticking, the heater cables, valve, or air flaps must be undesirable. First be sure the completed cooling equipment is working magnificent, because of the fact the engine temp is lots greater significant then the passenger temp. the two radiator hoses could desire to be chilly once you first initiate. the backside you would be able to desire to slowly get heat, collectively as the precise maintains to be chilly till the engine is completely as much as temperature. Then all of sudden the thermostat could desire to open and the precise hose could desire to get too warm for convenience. If no longer, then you definately the two have low coolant, undesirable thermostat, or air blockage. Then examine the heater valve and controls. there'll the two be a cable or vacuum hose from the administration interior, to the valve interior the engine compartment. Have somebody watch collectively as you utilize the administration lower back and forth from severe to low. If the valve isn't making finished circulate, then the cable must be slipping or badly adjusted. whether this is vacuum controlled, there must be leak or blockage. Air flaps are greater stable to tell because of the fact they do no longer seem to be so seen, and that i do no longer endure in ideas lots what they seem to be. yet lower back circulate controls and look ahead to reaction at flap hands and levers.

Answer 5

check the air compressor my car started doing that and then it went to blowing hot air all the time i had to replace to air compressor.

Answer 6

It either needs coolant or your compressor is going out. Mine did that, it was the compressor!

Answer 7

cycling switch

Answer 8

need freon