Fogging of Windows in the Defrost Mode - kw air condition A/C front HVAC operation performance window windshield

When servicing the vehicle with the VIN you entered, the following diagnosis might be helpful if the vehicle exhibits the described symptoms.

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 in the powertrain section under the engine data 2 data list. If the high side pressure is excessive, the PCM will command recirc operation via class 2 to the HVAC control head. It will not matter what mode is selected. The compressor does not have to be on to have this occur. Inspect circuit 2700 (terminal 2); it could be swapped with circuit 2751 (terminal 1) at the 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 recirc 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.

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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. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance. This diagnostic approach was developed for the vehicle with the VIN you entered and should not be automatically be used for other vehicles with similar symptoms.

( 03-04 Chevrolet Silverado) and (03-04 Chevrolet Avalanche) and (03-04 Chevrolet Tahoe, Suburban) and (03-04 GMC Sierra, Sierra Denali ) and (03-04 GMC Yukon, Yukon XL, Denali, Denali XL ) and (03-04 Cadillac Escalade, EXT, ESV )

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