The Instrument Panel Module (IPM) can control three purge modes depending on outside air temperature, inside air temperature and engine coolant temperature conditions at engine start-up. These purge modes are:
| • | Normal Purge |
| • | Cold Purge |
| • | A/C Purge |
When the system is powered up, it is desirable to purge the system of stale air or to redirect the air to avoid window fogging or icing. When the ignition is turned ON and the HVAC system is in the AUTO mode, the IPM will evaluate the startup conditions. The IPM will then select the appropriate purge mode to minimize the undesirable condition.
Normal
Moisture tends to accumulate in the HVAC module assembly after the engine has been shut off. When the engine is restarted and the A/C system turns on this moisture may be expelled from the windshield or instrument panel outlets and cause window fogging.
On start-up the IPM checks for indications that this may occur. If the IPM determines that window fogging can occur, the mode actuator moves to the floor mode to direct most of the stale moist air to the floor for a few seconds. The blower runs at low speed during normal purge.
Cold
In cold weather, moist breath air from vehicle occupants may freeze on the windshield.
On cold engine start-up, the IPM checks for indications that this may occur. If so, the IPM positions the mode doors to direct air out of the windshield outlets and operates the blower at low speed to keep the occupants breath off the windshield.
Cold purge mode is bypassed if any manual blower or manual mode is chosen.
A/C
Moisture tends to accumulate in the HVAC module assembly after the engine has been shut off. When the engine is restarted and the A/C system turns on, this moisture may be expelled from the instrument panel outlets toward the front seat occupants.
On start-up, the IPM checks for indications that this may occur. If so, the IPM positions the mode doors to direct air toward the floor outlets. The blower motor operates for a few seconds.
