Intermittently A/C Blows Warm At Start Up - keywords blows compressor cooling fan high hot hvac inoperative low pressure

This PI Supercedes To Add Fix Information. Please discard PIT4064.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Some owners may comment that when restarting the vehicle, after being shut off for up to 7 minutes the a/c blows warm. This concern will only last 2 or 3 minutes after the vehicle is restarted and then start operating properly. During this time the engine cooling fans will not operate. To duplicate this concern, the vehicle needs to be shut off when the engine cooling fans are on "HIGH" speed and then restarted within 7 minutes. After start up the A/C compressor will be on, but the engine coolant fans will remain off even if the high side pressure reaches the turn on pressure of 210 psi/265 psi (1447 kPa /1837 kPa). If the high side pressure reaches 429 psi (2958 kPa) the A/C compressor will turn off and also the A/C LED on the control head will turn off. The A/C compressor will continue cycling at the high pressure cutoff until the cooling fans come back on. Also, during this time, if the cooling fans are commanded "on" by using the TECH 2, they will not operate. There will be no DTCs and after approximately 2-3 minutes the engine cooling fans will turn on and the A/C will start to operate properly.

Note: If the vehicle is shut off with the engine cooling fans in "LOW" speed or "OFF" or sits longer than 7 minutes after key off, the cooling fans will operate normally and there will be no A/C performance concerns.

To correct this concern reprogram the ECM with updated calibrations currently available in TIS2000. As always make sure your Tech 2 is updated with the latest software version.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.