1995 Chevy Corsica Top Vents Only

1995 CHEVROLET TRUCK
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DIGGERDU
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  • 1 POST
I have a 1995 Chevy Corsica with 109,600 miles. I only have air blowing out of the top vents. It doesn't matter what heat/AC position I have selected. I have no defrost, no bottom heat. The fan blows normal at any speed, just can't select where the air blows to. Even when fan and heater is shut off, air still comes out of top vent. Any help would be greatly appreciated.

Jim (diggerdu)
Dec 28, 2006 at 3:23 PM
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MATHIASO
  • ✓Experienced Mechanic
  • 1,209 POSTS
It could be "flap" or "damper" not moving to redirect the air. Sometimes they are electrical in nature or vacuum(older ones are usually cable directed). A bad switch or jammed flap are reasonable possibilities.
Jan 8, 2007 at 2:53 AM
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2CARPRO JACK
  • ✓Experienced Mechanic
  • 11,533 POSTS
Check the vacuum lines under the hood. Sounds like a supply problem, GM defaults to defrost when insufficient vacuum is present to control the blend doors
Jan 8, 2007 at 9:22 AM
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Suggested Repair

Check the underhood vacuum supply lines that control the HVAC mode doors. Insufficient vacuum can leave the doors stuck so air only exits the dash vents. Also inspect the mode-door flaps or actuators for a jammed damper, and consider a faulty mode switch.

Conversation Summary

A 1995 Chevrolet Corsica owner reports airflow only from the top vents in every heat and A/C position, with no defrost or floor heat. The blower speed is normal, and some air still comes from the top vent with the fan and heater off. Experts suggest a mode door or damper that is not moving, possibly from a vacuum supply problem, a bad switch, or a jammed flap. One notes that GM systems often default when vacuum is insufficient and recommends checking the vacuum lines under the hood.

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