System Purges

SYSTEM PURGES
When the system is powered up it is desirable to purge the system of stale air and/or redirect the air to avoid window fogging or other undesirable conditions. When the ignition is turned on and the HVAC system is in the auto mode, the programmer will determine if any of the undesirable conditions exist. The programmer then has the option of three different purge modes to select from 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. If so, the programmer delays blower operations for five seconds, energizes the heater solenoid to direct air toward the floor, and runs the blower at low speed for fifteen seconds. The programmer then resumes normal system operation.
Normal purge mode is bypassed if the fan is operating in manual mode or if DEFROST mode is chosen at start-up.

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 energizes the A/C solenoid to direct air out the windshield outlets and runs the blower at 60% of maximum speed for twenty seconds. The programmer then resumes normal system operation.
Cold purge mode is bypassed if the fan is operating in manual mode or if DEFROST mode is chosen at start-up.

A/C PURGE
Moisture tends to accumulate in the heater and A/C module assembly after the engine has been shut off. When the engine is re-started 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 energizes the heater solenoid to direct air toward the floor, and runs the blower at 80% of maximum speed for four seconds. The programmer then resumes normal system operation.
A/C purge mode is bypassed if the fan is operating in manual mode or if DEFROST mode is chose at start-up.