2004 Chevy Trailblazer Front vents don't work

Tiny
ROCK09
  • MEMBER
  • 2004 CHEVROLET TRAILBLAZER
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 185,000 MILES
Changed alternator in winter since then front vents don't work. Blower motor and floor and defrost vents do work. Just the front vents are dead completely

any ideas and at what cost to repair
Wednesday, May 5th, 2010 AT 11:18 AM

1 Reply

Tiny
FACTORYJACK
  • MECHANIC
  • 4,159 POSTS
Is this a manual or automatic climate system? Does defrost and floor always blow together, at the same time, or does the system transition from floor to defrost when selected. Without a scan tool, it could be kind of a shot in the dark, you could have a faulty actuator, or climate panel/module. You can try a recalibration on the system, but first disconnect the battery cables and short them together for 10 seconds or so to deplete voltage. The procedure is as follows:

Actuator Recalibration (Primary)
When replacing the HVAC control module it will be necessary to allow the HVAC control module to perform a calibration process. When installing the HVAC control module be sure to perform the following:

Important: Do not adjust any controls on the HVAC control module while the HVAC control module is self-calibrating. If interrupted, improper HVAC performance will result.

Place the ignition switch to the OFF position.
Disconnect the scan tool.
Install the HVAC control module.
Connect all previously disconnected components.
Start the vehicle.
Wait 40 seconds for the HVAC control module to self-calibrate.
Verify that no DTCs have set as current DTCs.
When replacing the HVAC actuator it will be necessary to allow the HVAC control module to perform a calibration process. When installing the HVAC actuator be sure to perform one of the following:

Important: Do not adjust any controls on the HVAC control module while the HVAC control module is self-calibrating. If interrupted, improper HVAC performance will result.

Alternate Method (w/o Scan Tool)
Clear all DTCs.
Place the ignition switch to the OFF position.
Install the HVAC actuator.
Connect all previously disconnected components.
Remove the HVAC B fuse for a minimum of 10 seconds.
Install the HVAC B fuse.
Start the vehicle.
Wait 40 seconds for the HVAC control module to self-calibrate.
Verify that no DTCs have set as current DTCs.
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Friday, May 7th, 2010 AT 11:45 PM

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