Auto-HVAC in OFF Blows High Defrost Air After Startup - kw AC air automatic blower CJ2 cool cold control defroster head heat high ignition module no off on operation part relay resistor temperature

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

Intermittently, the Automatic HVAC goes to HI blower speed even though the system is in OFF position.

If a CJ2-Automatic HVAC equipped vehicles system was turned off prior to shutting the vehicle off and re-started later, the fan may blow high speed defrost air until any button on the HVAC control is selected. Beginning with the 2000 model year a change to the operating software in the control head for it to go to a mid-high blower speed with defrost and about 15% floor even with the HVAC control head shut OFF on an initial start-up with enough change in temperature from shut-off to start-up. SPO parts inventory was purged of the previous design software control heads, so when a customer initially takes their 1998-1999 vehicle in for a repair, they will get this updated logic if the control head is replaced.

This condition is normal and is operating as designed. The change was made to reduce the possibility of condensation forming on the windshield on startup when the climate controls were in the OFF position.

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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.

(98, 99, 00 Pontiac Grand Prix)

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