2003 Pontiac GT1 3.4

The rear defrost is an electric switch for the defroster in the rear glass.
If you turn on the ac and do not get cold air, the first thing to check is if the compressor is running. If not, you could be low on freon or have an electrical problem in the circuit for the ac clutch.
If the compressor is running and one of the ac lines is ice cold, you could have a blend door problem under the dash.

My 2003 Toyota Camry AC often starts blowing hot air and the AC light starts blinking. I don't know why the following process works, but it does. Using the temp selector (left) reduce the temperature all the way down to Max Cold and then push the Auto button. It will start blowing out very cold air. After a little while push the temp selector to the desired temperature.

you say it will blow cold and hot air for only a few minutes. You don't say but I assume you mean will blow cold a few min. when turned on AC max , blow hot only a few min. when turned to heater hot. Assuming thats the situation and you say AC charged and shows good on the low side -you should charge the AC to a full charge on the low side will cause problems with the AC air compressor kicking on and off. I suggest while the engine is running and turned to AC cold max watch the AC air compressor clutch to see if it does indeed kick on and off if so charge completely. As far as the heater make certain you coolant is all the way to the top and the best way to do this is when engine is completely cold remove radiator cap and fill completely and completely close cap then fill overflow container just to the cold level. That should fix your problem.

sounds like you need to have your AC serviced, alot of times the compressor wont kick on when you are low on freon.

I would check the following possibilities:
1. Is compressor clutch working? - You need to do this when the ac is blowing hot air only - locate compressor drive pulley on engine - rubber belt wraps around it. Start engine and set to max ac. When the ac is blowing hot air, look at the center of the compressor drive pulley using a good flash light - watch it for a while, it should be spinning with the pulley - this means the compressor is engaged. If not, the compressor is not engaged. If your ac is blowing hot air, then the compressor should be engaged and running (trying to cool). If it is not engaged, then your compressor clutch is probably going out. Could be low voltage to clutch, but more likely the clutch is worn out and only working some of the time. Note: if working normally, the compressor clutch will engage and disengage in cycles- but the air should always be cold. If clutch is bad, compressor would need to be replaced (sold as one unit). This is tricky to diagnose and could take some time - you need to do it when ac is blowing hot air but set to max cooling.

2. Low on refrigerant or refrigerant has moisture in it? If your ac blows cold initially after being off for a while, then heats up, and continues to regularly cycle back and forth between hot and cool air, then the system may be low on refrigerant or the refrigerant may have moisture in it that is freezing and restricting refrigerant flow. An a/c shop can check refrigerant level and even replace refrigerant if moisture is suspected.

Could be other issues, but I would start with these.

Good luck

The low side pressure seems ok the high side would help,Is your compressor cycling and is the air coming out even slightly cool?slight over charge cold effect cooling ability.I wish I could be more help. I will have to think about this one.maybe you could make sure your temp.door is actually in the commanded cold position.

YES THE AC SYSTEM IS LOW ON REFRIDERENT. U HAVE A LEAK SOMEWHERE.

When you say tinker with the A/C. what did he do??? Just want to make sure he did not hot wire anything to activate the compressor at the max position. If the system is low on compressor oil the compressor will not active to keep it from getting damage or low on R143A. Most place now will recharge the A/C system for $50.00 since they know that you can by a recharge kit for around the same price, but you need make sure you don't over charge the system or damage will occur. If you not familiar with the recharge procedure, have it recharged by a shop and if it's full then the problem may be a  pressure switch and that takes around 5 min to replace and i am sure the shop will let you know before they try to recharge the system by hooking up the gauges to read the pressure in the system. Good luck and keep me posted, be glad to help you get some cold air again. 

not a home mechanic job thats for sure ,check youre pollen filter isnt choked up if thats ok then you need a specialist repairer because the venturi offrice is blocked which means that the high pressure gas isnt going through the small hole causing it to stay hot.must ge er indoors moaning

make sure you compressor is kicking on. find you a/c compressor. there should be a gear on the front of it. DO NOT touch it. turn the a/c on high and max look at the gear see if it kicks on and off.
Just DO NOT get your hand in the way just incase the gear does kick.