The owner of a 2008-10 Chevy Cobalt or Pontiac G5 or 2008-11 Chevy HHR may come into your store with a complaint that his A/C system blows nothing but warm air. When you open the hood, you may find that the a/c clutch isn't engaging when the switch on the dash is activated.
What's causing the problem?
To find out, connect your scan tool, check for trouble codes related to the a/c system and repair as necessary. If no codes pop up on the tool's display, go into the data stream and look at the following PIDs: AC Request, AC Relay Command and AC Pressure Sensor. If you see "No" next to the first two PIDs and zero pressure from the pressure sensor, you're likely dealing with a BCM that was improperly set up during a previous repair, says GM.
To turn things around, try enabling the AC option in the BCM with your scanner. If the option isn't listed on the display, the module is shot and needs to be replaced and set up correctly. Check with a dealer for the specifics.
"Factory Fixes" is written by Jim DePalma, a 30-year veteran of the auto repair business who has served stints as a service manager, parts manager and ASE-certified technician. His column provides vehicle manufacturers' authentic factory technical service bulletins (TSBs) that have been condensed for easier reading. Mr. DePalma advises that techs always check with a dealer or repair information system for the latest revisions before starting to work on a vehicle. He can be reached via email at [email protected].