System Purges

The HVAC programmer can also access three additional "purge" modes when certain conditions exist.

When the system is powered up, it is desirable to "purge" the system of stale air and/or redirect to avoid window fogging or other undesirable conditions. When the ignition is turned on and the HVAC system is in the AUTO or ECON mode, the programmer will determine if any of the undesirable conditions exist. The programmer then has the option of selecting three different purge modes in order to eliminate the undesirable condition.

Normal Purge

Moisture tends to accumulate in the heater and A/C 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 programmer checks for indications that this may occur. The programmer will delay blower operation until the engine coolant temperature reaches 38°C (126°F), and closes the defroster door, positions the A/C door to direct air out the heater outlets, and runs the blower at low speed for 30 seconds. The programmer then resumes normal system operation.

Normal purge mode is bypassed if the fan is operating in manual mode or any manual mode is chosen.

Cold Purge

In cold weather, moist breath air from vehicle occupants may condense on the windshield.

On cold engine start up, the programmer checks for indications that this may occur. If so, the programmer positions the doors to direct air out the windshield outlets and runs the blower at 60% of maximum speed for 30 seconds. The programmer then resumes normal system operation.

Cold purge mode is bypassed if the fan is operating in manual mode or any manual mode is chosen.

A/C Purge

Moisture tends 10 accumulate in the heater and A/C 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 front seat occupants.

On start up, the programmer checks for indications that this may occur. If so, the programmer positions the A/C door to direct air toward the floor and runs the blower at 64% of maximum speed for seven seconds. The programmer then resumes normal system operation.

A/C purge mode is bypassed if the fan is operating in manual mode or any manual mode is chosen.