Finding the cause of battery drain can be tricky, but sometimes your ears will help you find the culprit. A Mitchell 1 SureTrack community member had a Chevrolet Impala in their shop because the owner complained that the battery kept going dead. The charging system checked out, but while working on the vehicle they heard some clicking sounds under the dash. The following Real Fix summarizes the interaction between members of the community that led to the solution.
Vehicle
2007 Chevrolet Impala LT 3.5L
Complaint
Customer states that battery goes dead while vehicle is sitting.
Diagnostic Steps Performed/Parts Replaced
Performed charging system test and all is normal. Shortly after the test, while looking for loose wiring, a clicking noise was found and appeared to be moving throughout the dash in a cycle. The temperature control doors were clicking, attempting to move, but were in fact stuck to one extreme. Scanned the HVAC system and retrieved three codes.
• B0223: Recirculate Position Command Circuit Actuator Stuck
• B0408: Left Air Mix Control Circuit Malfunction Actuator Stuck
• B0418: Temperature Control 2 Circuit Actuator Stuck
Best Answers from Community
Try commanding the motors with the scan tool to see if they operate. When they reach the end of their travel, the module sees the increase in amperage and turns them off. With the plastic worm gear worn off, there is not enough load to raise the amperage so they continue to run. You can replace just the one that is ticking, then reevaluate. It’s not abnormal for them to set a code and still work fine.
Cause
Cannot command the motors — replaced two of the motors and still cannot command them. Internal failure of the controller causing motors to run with key removed, draining the battery.
Correction
Replaced HVAC control module and three bad mode door actuators. No more clicking noise and battery not draining with key off.
Courtesy of Mitchell 1 ProDemand SureTrack.
