EI06031 - HVAC Unable to Change Modes or Temperature, Inoperative, Poor A/C Performance (Reset HVAC Control Head)

This bulletin is being revised to provide field fix information. Please discard Corporate Bulletin Number 06-01-39-004B (Section 01 - HVAC).

Some customers may comment that they are unable to change the HVAC mode and/or temperature. Customers may also comment that the A/C may be inoperative or have poor performance.

Engineering has determined based on technician feedback, that this concern may be caused by not having the updated HVAC control module software or due to a communication issue between the temperature door actuator and the control head.

HVAC Inoperative/Can't Change Mode/Can't Change Temperature

1. Verify that the HVAC Control Module software is no older than P/N 1588619*.

* There are multiple calibration part numbers, based on vehicle configuration. The last digit of the part number will vary.

2. Reprogram, if the software is not the latest version.
3. If reprogramming corrects the customer concern, no further action is necessary. If reprogramming does not correct the customer's concern, proceed to the "Poor Performance" section of this bulletin.

Poor Performance

If the air temperature does not meet performance specifications; one possibility for this is that the temperature door within the HVAC module is not at full cold position, even though the scan tool/Tech 2® may indicate zero counts. This is caused by a communication problem between the temperature door actuator and control head software. Engineering is working to develop and validate a service calibration to correct this concern. Until the service calibration is available, use the following steps as a short-term resolution.

Important: This is a short-term repair. This bulletin will be updated when the service calibration is available.

1. Turn the temperature control knob on the HVAC control head to full hot and back to full cold two times.

Important: Be sure to allow enough time for the door to move to full hot position before moving it back to full cold.

2. Disconnect (unplug) the HVAC control head.
3. Wait 10 seconds.
4. Reconnect the HVAC control head.

For vehicles repaired under warranty, use: