B1919-17

B1919-17-BLOWER MOTOR CONTROL - CIRCUIT VOLTAGE ABOVE THRESHOLD

For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

A Blower Motor Power Module allows the microprocessor-based A/C Heater Control to calculate and provide infinitely variable blower motor speeds based upon either manual blower switch input or the ATC programming. The ATC blower motor control system uses a Pulse Width Modulated (PWM) circuit strategy. PWM voltage is applied to a comparator circuit which compares the PWM signal voltage to the blower motor feedback voltage. The resulting output drives the power module circuitry, which provides a linear output voltage to change or maintain the desired blower speed.

- When Monitored:
With the ignition on.

- Set Condition:
If the A/C Heater Control detects a short to voltage or open on the Blower Motor Control circuit. If a valid voltage is detected the DTC will change from active to stored and stay in the controllers memory for 100 consecutive ignition cycles.





Always perform the HVAC Pre-Diagnostic Troubleshooting procedure before proceeding. Initial Inspection and Diagnostic Overview.

1. CHECK IF DTC IS ACTIVE
1. Ignition on, engine not running.
2. With the scan tool, read HVAC DTCs.

Is this DTC active?

Yes

- Go To 2

No

- Go To 6

2. CHECK THE (C) BLOWER MOTOR CONTROL CIRCUIT FOR A SHORT TO VOLTAGE
1. Turn the ignition off to the lock position.
2. Disconnect the Blower Motor Power Module harness connector.
3. Disconnect the A/C Heater Control harness connector.

NOTE: Check connectors - Clean/repair as necessary.

4. Ignition on, engine not running.
5. Check the voltage of the (C) Blower Motor Control circuit.

Is there any voltage present?

Yes

- Repair the (C) Blower Motor Control circuit for an short to voltage.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Go To 3

3. CHECK THE (C) BLOWER MOTOR CONTROL CIRCUIT FOR AN OPEN
1. Turn the ignition off to the lock position.
2. Measure the resistance of the (C) Blower Motor Control circuit between the A/C Heater Control harness connector and the Blower Motor Power Module harness connector.

Is the resistance above 1.0 Ohm?

Yes

- Repair the (C) Blower Motor Control circuit for an open.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Go To 4

4. CHECK THE (CC) BLOWER MOTOR CONTROL RETURN CIRCUIT FOR AN OPEN
1. Measure the resistance of the (C) Blower Motor Control Return circuit between the A/C Heater Control harness connector and the Blower Motor Power Module harness connector.

Is the resistance above 1.0 Ohm?

Yes

- Repair the (C) Blower Motor Control Return circuit for an open.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Go To 5

5. CHECK THE BLOWER MOTOR POWER MODULE
1. Turn the ignition off to the lock position.
2. Replace the Blower Motor Power Module. Blower Motor Power Module - Removal
3. Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

Did the DTC reset during or after the HVAC Verification Test?

Yes

- Replace and program the A/C Heater Control. A/C And Heater Control - Removal.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Test complete.

6. CHECK THE WIRING AND CONNECTORS
1. The conditions necessary to set the DTC are not present at this time.
2. With the scan tool, check the Environmental Data to help identify the conditions in which the DTC was set.
3. Using the wiring diagrams as a guide, check all related splices and connectors for signs of water intrusion, corrosion, pushed out or bent terminals, and correct pin tension.
4. Wiggle the wiring and connectors while checking for shorted and open circuits.

Were there any problems found?

Yes

- Repair as necessary.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Test complete.