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B1905-15






B1905-15-MAIN/LEFT TEMPERATURE DOOR 1 SENSOR CONTROL - CIRCUIT SHORT TO BATTERY OR OPEN





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

Theory of Operation

After the initial installation of the A/C Heater Control, the controller is calibrated to each individual blend/mode door actuator. The actuators are connected to the A/C Heater Control by a dedicated five-wire sensor and control circuits. The actuator can move the blend/mode-air doors in two directions. When the A/C Heater Control pulls the voltage on one side of the control circuit high and the other low, the door actuator will move in one direction. When the A/C Heater Control reverses the polarity of the voltage to the motor, the blend door actuator moves in the opposite direction. Once the A/C Heater Control makes the voltage to both control circuits high or low, the door actuator will stop its movement and stay in that position. The blend/mode door actuator contains a three wire potentiometer, which the A/C Heater Control uses to monitor the relative position of the blend/mode air doors. The A/C Heater Control learns the blend-air door stop positions during the calibration procedure.

- When Monitored:
Continuously with the ignition on.

- Set Condition:
The A/C Heater Control detects a short voltage on the Blend Door Sensor circuit. If the A/C Heater Control detects a valid voltage, the DTC will change from Active to Stored and will stay in the controllers memory for 100 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 running.
2. Using the HVAC controls, switch to full hot and full cold and then back again.
3. With the scan tool, read HVAC DTCs.

Is this DTC active?

Yes

- Go To 2

No

- Go To 7

2. CHECK THE (C36) BLEND DOOR SIGNAL CIRCUIT FOR A SHORT TO VOLTAGE




1. Turn the ignition off to the lock position.
2. Disconnect the A/C Heater Control harness connector.
3. Disconnect the Blend Door Actuator harness connector.
4. Ignition on, engine not running.
5. Measure the voltage of the (C36) Blend Door Signal circuit.

Is there any voltage present?

Yes

- Repair the (C36) Blend Door Signal circuit for a short to voltage.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Go To 3

3. CHECK THE (C36) BLEND DOOR SIGNAL CIRCUIT FOR AN OPEN




1. Turn the ignition off to the lock position.
2. Measure the resistance of the (C36) Blend Door Signal circuit between the A/C Heater Control harness connector and the Blend Door Actuator harness connector.

Is the resistance above 5.0 Ohms?

Yes

- Repair the (C36) Blend Door Signal circuit for an open.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Go To 4

4. CHECK THE (C121) SENSOR GROUND CIRCUIT FOR AN OPEN




1. Measure the resistance of the (C121) Sensor Ground circuit between the A/C Heater Control harness connector and the Blend Door Actuator harness connector.

Is the resistance above 5.0 Ohms?

Yes

- Repair the (C121) Sensor Ground circuit for an open.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Go To 5

5. CHECK THE (C36) BLEND DOOR SIGNAL CIRCUIT FOR A SHORT TO THE (C26) 5-VOLT SUPPLY CIRCUIT




1. Measure the resistance between the (C36) Blend Door Signal circuit and the (C26) 5-Volt Supply circuit.

Is the resistance below 100k Ohms?

Yes

- Repair the (C36) Blend Door Signal circuit for a short to the (C26) 5-Volt Supply circuit.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Go To 6

6. CHECK THE BLEND DOOR ACTUATOR
1. Turn the ignition off to the lock position.
2. Replace the Blend Door Actuator. Blend Door Actuator - Removal.
3. Reconnect all previously disconnected connectors.
4. Ignition on, engine not running.
5. Using the scan tool, erase HVAC DTCs.
6. Using the scan tool, perform the HVAC Actuator Calibration Test.
7. Turn the ignition off to the lock position for 30 seconds.
8. Ignition on, engine running.
9. Using the HVAC controls, switch to full hot and full cold and then back again.
10. With the scan tool, read HVAC DTCs.

Did this DTC reset?

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.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

7. 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.

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