185K Miles and after driving about 45-60 minutes the AC stops blowing cold air. The blower inside the car runs, the clutch is still engaged on the compressor yet only warm air is blowing through the vents. If the car sits overnight the AC will work again. It does not always stop after 60 minutes of driving. Sometimes I can go days driving 60 minutes at a time and the AC works the entire time. Other times it will quit after 45 minutes. When it works I have no complaints. Any ideas?
Take it to a qualified automotive A/C repair technician. They have the proper equipment and expertise to diagnose and repair the system… and comply with relevant EPA regulations.
In order for the inside of the car to get cooler, heat has to vent to the outside somewhere. The AC system takes the heat from the inside, and transfers it to the engine compartment. There’s a fan in the engine compartment that is supposed to blow the heat away. If that fan isn’t working, this would be a symptom. Ask your mechanic to check the engine fans. On some cars there is an rpm spec for them too.
It’s extremely diffiult to diagnose an A/C problem over the internet without knowing the high and low side pressures, what the pressures are at certain RPMs, etc.
This problem could be due to an evaporator freezing up for any one of a number of reasons. If freezing is suspected, look underneath the car on the passenger front and note if water condensation is dripping out. If not, turn the A/C off and operate the heater for a few minutes.
If water starts flowing freely after a few minutes of heater use then the evaporator is freezing.
More than likely the expansion valve is malfunctioning.
The expansion valve is what meters the refrigerant into the evaporator which creates the cooling effect.
Because the refrigerant is under very high pressure at the expansion valve, this causes the refrigerant to become hot. This heat then causes the expansion valve to malfunction where it doesn’t meter the refrigerant correctly into the evaporator so the AC no longer cools.