EI07264 - Manual HVAC Performance, Temperature, Mode, A/C Does Not Cool, DTC B0228, B0413, B0423, B0433, B3779, B3782 (Engineering Information)

This bulletin is being revised to update the diagnostics. Please discard Corporate Bulletin Number 07-01-38-009 (Section 01 -- HVAC).

Important: 

Some customers may comment that the A/C blows hot air or is inoperative. They may also comment that they are unable to change the temperature or HVAC mode of the vehicle. In this instance, the actuator door defaults to full hot and defrost position.

GM Engineering is seeing an increase in HVAC control head and actuator warranty where the root cause is intermittent wiring connections at the actuator, control head or the right hand BEC.

GM has a need to obtain information BEFORE any repairs are made. If the customer's concern can be duplicated, perform the following inspections/steps:

1. Note the following information on the repair order:

1.1.	Describe the customer's concern -- be specific.

1.2.	List any/all DTCs and note whether the DTC is current or stored in history.

1.3.	Note Door position (feedback) counts from the Tech2.

Important:  The concern must be current before diagnosis can be performed.

2. Review and print the following SI documents -- Electrical Center Identification Views, for use during diagnosis:

•	Junction Block -- Right I/P, Top View

•	Junction Block -- Right I/P X4

•	Junction Block -- Right I/P X5

3. Locate the Junction Block -- Right Side I/P on the vehicle.
4. For the appropriate actuator, measure the following signals for voltage/resistance from the BACK of the X4 or X5 connector and record the following:

Important: DO NOT unplug the X4/X5 connector.

Turn Ignition On, A/C Blower Full, if possible -- mode on "panel" and Temp to "cold."
Actuator will stay in default position until commanded to a new position. Change commanded position regularly to see if issue is still current.
Continue to monitor door positions (feedback) on Tech2 to see if it changes during circuit testing.

•	Ignition Voltage -- 12V

•	Door Control Signal -- 2.5V when stationary, 0V when commanded toward "cold" or "panel", 5V when commanded toward "hot" or "defrost"

•	Low Reference -- less than 40Ω

•	Door Position Signal -- measure voltage

•	5 Volt Reference -- 5V

5. If any signals do not display the correct value or if the issue is corrected during testing, pull the connector and check the terminal for poor tension (use the appropriate terminal tool). Replace or repair the terminal if poor tension is found.
6. If all signals are correct and the issue is still current, locate the appropriate actuator and check the signal performance at the BACK of the actuator connector.
7. Contact engineer Adam Freeman at 586-914-0404 and provide him with repair order information. If necessary, Adam will provide information to proceed with correcting the customer's concern. If the engineer is not available to take the call, leave the following information:

- Technician Name, date and time of call

- Dealer Name, Dealer Code & Phone #

- VIN and Repair Order #

Important: If the engineer does not return the call within one (1) hour, continue to diagnose and repair following the information found in SI. Fax the front and back of the repair order to Adam Freeman (fax #: 248-685-4196).

For vehicles repaired under Engineering direction, use: