On my 2004 Trailblazer the air conditioning works fine and blows nice cold air when the car is first started and "cold". When it is warm and has run for a while the air still works fine, until you turn it off, and try to turn it back on while the engine is at proper operating temp. Then the compressor will not turn on again and it blows hot air. If the car is cooled off overnight or so and the air is turned on before you start the car it the compressor turns and the air is fine. However if you start the car and then try to turn the air on the compressor clutch does not turn the compressor on and it blows hot air. I am 80 years young, been working on cars all my life, and enjoy trying to fix them but I have slowed down a little................Any ideas would be appreciated. Thank you........

 

You could be borderline on refrigerant. That would explain why it is cold, then after it is shutoff, no compressor. I believe on yours it has a low pressure compressor cutoff switch. i could be a smart alec, and just tell you to not shut it off

 

I will get some Freon and try that. I have not shut it off for several
weeks while it was hot, but when I turned the fan off at night, it
turned it off for me and I could not get it to come back on while the
car was hot. Next day it comes right on. I thought maybe the clutch
was worn a little. Do you know the gap at the clutch plate when its
off? Maybe if it is off I can get the clutch plate off and remove one
of the adjustment washers and correct the gap.
You are not a smart alec when you are trying to help, and I
appreciate your effort.
Catch

 

the refrigerant could be low or the compressor may be tired.

have the system filled by a shop. home filling it terribly inaccurate.

if the problem still occurs with the system filled properly; rev the engine up to 2500rpm and hold it at that speed. if the system goes from hot to cold...the compressor is done.