Tuesday, April 17, 2012

Chevy HVAC Controls Not Working After Battery Disconnect?

This Problem is noticed on Chevrolet TrailBlazer.
the HVAC control system stopped working after disconnecting battery and reconnecting.
The System just works on full head and mode actuator to full defrost.But the controls are not able to lower the head or defrost.

On this basic the troubleshooting details for this problems are as follows:----

This is a common occurrence on the Trailblazer. What happens is over time the actuators that move the mode, temperature and recirculate blend doors will wear. The wear will allow the actuators to move outside the normal limits. This however is not realized until battery power is lost. On power up, the system recalibrates the actuators sweeping them to their full limits of travel. Then the control module sees that the actuators travel beyond their normal limits. The control module then puts the actuators into a default mode. Temperature actuator will go to full heat. Mode actuator will go to defrost. The fix for this problem is to replace the actuators. The mode and drivers side temperature actuator can be replaced from under the dash. Passenger side temperature actuator (for dual temp systems) and recirculate actuator can only be replaced by removing the dash.

This job takes 3-4 hours normally.

Actuators are normally $125-150 each.There are 3 actuators so you are looking at 3 x $150.

The battery must be disconnected for some types of repair work, so sometimes it is unavoidable. If a shop has never experienced this before, they would not know what problems may result from just disconnecting the battery. This is not something that is published in the repair manuals. This is something we learn the hard way at our garage.This is very much noticed on Chevy trailblazer models.Once at our garage , Disconnected a customers battery to make repairs and then they come back saying their a/c isn't working. Had to replace actuator for free that day to keep customer happy.But it was near to failing actuator.

Also read this more help detail:--
The high heat overrides the air conditioning.

You can remove the temperature actuator and manually turn the heat blend door to the cold position. Or you can disconnect power ( or pull fuse ) to make the system recalibrate, then disconnect the temperature actuator connector while it is in the Cold position. Then it will stay there.

This will help.

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