Chart 1 No Blower Operation/Improper Blower Speed

CIRCUIT DESCRIPTION

The airflow is controlled by modulating the commanded blower voltage which varies the blower speed. Under automatic control blower adjustments are made based on vehicle speed, coolant temperature, and the sun load sensor. There are special cases which may override the normal operation of the blower to limit snow ingestion, purging air ducts, cooling the instrument panel cluster, or enhancing heater warm-up performance.

TEST DESCRIPTION

If the blower is inoperative in normal operating procedure, but operates properly in override, the IPC or data line between the IPC and heater and A/C programmer would be suspect.

1. Checks the blower control output to determine if the heater and A/C programmer is sending voltage to the blower or if the problem could be in the circuitry.
2. Checks the heater and A/C programmer to determine if output is correct and looks at the input to the blower motor to check for opens in the circuit. If input and output are similar, it indicates a problem with the speed control within the blower assembly.
3. Since the automatic control operation of the blower undergoes adjustments based on vehicle speed, coolant temperature, and the sun load sensor, a properly operating blower may be controlled improperly.