Heater switching from the vent to the floor at idle

[Gumby87]

this is a little weird but going down the road heat blows out of the vent fine but when i pull up to a stop or the car is idling the heat will switch to the floor on its own what the heck causes this?

 

[Geesie]

Your heat blows out the mid vents? :?:

 

[Gumby87]

yes the heat will blow out of the vents floor or defrost but when it is on vent it will switch to the floor when pulling up to a stop or at idle

 

[busdriver]

Sounds like a vacuum leak or a bad vacuum control switch. Check for a hissing noise under/behind the dash or a broken/damaged vacuum line in the engine bay.... good luck.....

 

[pokertramp]

Make sure you have the vacuum line for the zone control on a constant vacuum. I think it is a purple line on all G-Bodies,not sure. If you have it on a different vacuum port it will only work under throttle.