Air flow issue - 99 Pontiac Grand Prix GT

[grandprix74]

Hi,
I have a grand prix and am having problems with the air flow. I think that the diverter is stuck/broke as air flow blows through all vents (defroster, 4 dash vents and floor). When I turn the switch that tells where the air to blow out, nothing happens. In the summer, the A/C works but since it comes out the floor vent my toes get cold. Does this sound like the diverter is stuck? Is there a way I could make the diverter only come out the dash vents? The car has 180K miles and I don't want to invest much money to fix this (i.e. taking to dealer). Thanks in advance for any help! Chris

[BNaylor]

Welcome to AF.

The HVAC vent actuators use engine vacuum that originates at the intake system. Called accessory vacuum. Symptom is abnormal airflow out of all vent registers at the same time or little or no airflow out the center vent registers but plenty out the floor and defrost vents.

So check the plastic vacuum line from the back of the upper intake manifold , along the firewall and where it wraps back to the battery and engine compartment fuse box. Also, there is a line coupler in that area that can get loose. From there it enters the firewall through the main wiring harness to the cabin.

[ccnewfelt]

i have a 98 and i have the same prob. still after i fixed all the vac. leaks..

[Tech II]

What system do you have? Manual/auto/dual?


there are different systems used....some have a vac switch in the control head....some have a vac sol box....some have a programmer.....some have a vac tank...the first thing you have to do, is check for vac, at either one of these points, with the car running.....if no vac is present, than something is open between there and the intake........