Cars is a 2002 with 39K and is not driven very much and I am a novice when it come to the A/C system. Blows cold air when going down the road but turns warm when sitting at a stop light. When the cars starts going again the air turns cold. Does this cycle every time. Any ideas?
Thanks

 

A/C fan turning on?

 

Could be low on R 134, freon. You can bone up on it and try servicing it yourself or take in into a reputable shop, does not have to be a dealer kind of thing.

Once it is up to speed, it is a good idea to turn it on every now and then to keep the seals in good condition.

 

Pretty sure both fans run on my MY06 car whenever the AC is on. Something to check.

-- Chuck

 

Make sure your cooling system isn't low on coolant. With a COLD engine remove the radiator cap and make sure the fins are covered. If they aren't and the reservoir isn't low then you could have a leaky head gasket. I had the same symptoms you're having on another car years ago and it turned out to be a leaky head gasket. When the A/C system gets too hot the pressure rises, kicking off the system. When the car is moving you're getting better heat removal in the engine compartment.

Also, make sure both fans are running when the A/C is on.

 

Thanks for the help: both fans turn on, oil looks nice and clean so we can rule out head gasket, next I will check the Freon level. Would it be a good idea to try the Freon cans with the gauge like the ones they sell at Auto Zone? The plug and play ones?

 

Get a manifold gauge with a service hose, any other method is guessing. The system pressure is critical for proper A/C function, too little and cooling will be weak, too much and the system will cut off to protect the compressor.

You want 42 to 57 cold side psi, that's a good range for Florida weather.

 

did ya fix it?

 

Still blowing warm are: low side pressure is around 55PSI, all vent functions seem to be working, both fans come on, compressor clutch engages when A/C button is pushed, and cabin filter looks new. This is a stumper.

 

How is the condenser? Sometimes cleaning out debris from there helps.

What about high side pressure? (Should be roughly 3x cold side pressure) There may be a restriction post condenser, either drier or expansion valve. Where not enough refrigerant is entering the evaporator, and as you increase engine speed it overcomes the restriction.