2001 Toyota Tacoma AC loses cooling

allenct · Posted at Thu Jul 02, 2009 6:37 pm

Air Conditioning problem
2001 Toyota Tacoma 4 cyl Two Wheel Drive Manual 128,00 miles

My AC unit loses cooling ability over a long drive. It works just fine for short trips of 15-20 minutes. If it is running for 20-30 minutes it loses its ability to cool. The fan works but blows warm air. When this happpens, if the truck sits for a while, the ac will work again. What might the problem be?

rasmataz · Posted at Thu Jul 02, 2009 9:21 pm

Faulty low pressure cutout switch. This switch prevents the compressor from running if the refrigerant level is low. If the cutout switch is not reading correctly, it can prevent the compressor from coming on.

Faulty compressor clutch. The magnetic clutch on the compressor requires full battery voltage to engage. If the voltage to the clutch is low, or the clutch coils have too much resistance, or the air gap in the clutch is too great, the clutch may not engage to drive the compressor.

Faulty compressor clutch relay. Check to see if the relay is receiving voltage when the A/C is turned on. Also check the relay wiring and ground connections. If bypassing the relay with a jumper wire or routing battery voltage directly to the compressor clutch makes the A/C work, the relay is probably bad.

Faulty A/C control switch. The switch may be worn and not making good contact when it is turned on.

Some possible causes of intermittent cooling (or no cooling) on automatic A/C systems include all of the above, plus:

A problem in the control module or control head (this usually requires using a dealer scan tool to read fault codes and perform self-diagnostics).

A bad temperature sensor (an ambient air temperature sensor, interior air temperature sensor, evaporator temperature sensor, or sunload sensor). Again, a factory scan tool is usually required to perform diagnostics on the system.