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When it stops blowing cold air check to see if the compressor clutch is still engaged. Maybe a problem with the hvac control switch
+1 with the above posts as well as using the manifold gauge set.
I would also check your a/c lines for icing. That could be an issue with your orifice tube/txv valve.
Keep us posted.
The likely cause is that the low pressure or the high pressure cutoff switches is engaging. If the system is overcharged or overheating then the high side switch will open. Since the system works great normally, it is unlikely that the low side pressure switch would be opening due to a low state of charge. This causes the air condition not to cool as well. Either low side or high side pressure switches could be malfunctioning. See the following information on the pressure switches.
http://www.realfixesrealfast.com/realfi … tches.html
Also, the problem could be related with the dash A/C button, wiring or control module associated with the climate control. If it isn’t reliably sending a signal to turn on the A/C, it will also cause the A/C not to operate properly.
Another problem could be with the A/C clutch and associated wiring back to the AC control module.
Try checking the operation of the cooling fans and there’s no way around this part you’re going to need to check the pressures with a manifold gauge set, if you don’t know what the pressures are in the system you can’t begin to diagnose it.
Quoted From EricTheCarGuy:
Were you able to check the cooling fan operation yet?
Update- The cooling fan worked on the compressor side of the car, put the manifold gauges on the system and the low pressure was still kinda low, high side was normal. Decided to replace the dryer, high/low switch, evaporator coil and the expansion valve. The system works great, but occasionally it stops blowing cold air and I shut it off and wait. Then it starts working again? Perhaps it is the compressor relay going bad?
What were your pressures? Why did you decide to replace those parts? This is why A/C work is not a normal DIY job.
What were the the high and low side pressures?
also need the aprox outside air temp for the day.
is the suction line sweating back?Im new to this HVAC stuff but I will put in my 2 cents anyway, and correct me if Im wrong but it sounds like you have an icing problem, to me.
Can I ask you to clarify exactly what is happening? When it stops blowing cold air, does it stop blowing air completely, or does it blow room temp air?
I think djhughs has it right– there should be a temperature sensor on the evaporator that will turn off the compressor if the evaporator gets too cold. If functioning properly, this will prevent ice-up. If the sensor fails, you’ll notice that the A/C slowly stops working as you drive, but will work again after it sits for a while (giving the ice a chance to melt.). Other symptoms you might notice are decreased airflow through the vents when the A/C is not working, increased blower noise and an unusually large puddle of water under the car from the evaporator drain after it has been sitting for a while. (the puddle is from all the ice melting away). The solution is usually to replace the sensor, but it’s always a good idea to check wiring as well.
BOTH fans need to work when the AC is on, if not AC performance will be compromised as it’s not able to move the heat like it should and it will exhibit the exact symptom you described, not cooling after running for a while.
Quoted From risacher:
Update- The cooling fan worked on the compressor side of the car, put the manifold gauges on the system and the low pressure was still kinda low, high side was normal. Decided to replace the dryer, high/low switch, evaporator coil and the expansion valve. The system works great, but occasionally it stops blowing cold air and I shut it off and wait. Then it starts working again? Perhaps it is the compressor relay going bad?
To answer your questions, I did not do the repair, but had a mechanic I know do the work. The low pressure side was around 14 psi, and the high was normal pressure. He added some freon and the low side went up to around 30 psi. The air worked for a couple hours then no cool air. Decided to replace the dryer, high/low pressure switch on the dryer, evaporator coil and the expansion valve. The air runs a lot longer than before, but still cuts off later on in the day. The air temperature is mid eighties. Both fans work and when it stops blowing cool air, the compressor is not turning. I shut it off on the dash and I continue driving. About 20 minutes later, I hit the on/off switch and it works!! Could it be a relay? My mechanic and I thought it was icing in the beginning, but the evaporator coil and hoses were not iced up. Any other thoughts?
It could be your compressor magnetic clutch was sticking , hit the clutch with a srew driver handle lightly when the problem occurs and see if it engage the compressor to run,if it does you have an intermitently stucking up clutch or check with a volt meter by pulling the wire connector on the compressor if you are getting 12 v in there then you have a electromagnetic clutch problem. And if your getting 0 volts then check your relay input/output
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