Fogging of Windows in the Defrost Mode - keywords air CJ2 CJ3 condition connector fog front HVAC operation performance sensor windshield wire

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

Customer may complain of excessive window fogging or unwanted HVAC recirculation in the defrost mode.

If this condition can be verified, inspect the high side pressure sensor with the Tech 2. This data is located under powertrain/data display/engine data display/engine data 2. If the high side pressure is excessive, the PCM will command recirculation via class 2 to the HVAC control head. It will not matter what mode is selected. The a/c compressor does not have to be on for this to occur. Inspect circuit 2700 (terminal 2) it could be swapped with circuit 2751 (terminal 1) at the a/c pressure sensor. This will make the Tech 2 data read between 375-385 psi for the a/c pressure sensor. This can be verified at key up or engine running. If the a/c pressure sensor is unplugged, the pressure will drop to zero. This turns the recirculation to the off position. Keep in mind, depending on the time of year, high a/c pressure or a faulty switch could also be a concern. Use A/C gauges to assist in diagnosis as necessary.

Note: 1 psi is equal to approximately .01 volts (example: 380 psi equals approximately 3.8 volts)

Please follow this diagnosis 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.