The front dash air vents do not blow air when in heat mode. The defrost vents work, the rear system also works. Using a combination of defrost, rear and heat to feet seems to heat the cabin okay. A/C works fine, new thermostat, pollen filters changed, no blockages observed. What could be causing this disruption in air flow?

SOURCE: No air flow from defrost vent on my van.

Could be a vaccum line leaking not changing the vent flap to defrost

SOURCE: The Air flows through only the defrost and feet vents

Inside the ventilation system there is gates that open and close to direct the air flow. These are operated on vacuum on most vehicles. The hose for that perticular gate may have disconnected somehow or has a hole in it. I suggest you take the heater controls out and see if there is a plug with a series of colored hoses on it. it so you'll have to trace each of them to see which one is the problem. Now you may be able to get some help from you local dealers mechanic who just may know the color code for that gate. (which would be a bonus) Good Luck

SOURCE: 1998 Olds Aurora, no heat, no air, just blowing air out the front

i beleive these are a vacuum system. if air temp is in cold position you will get no heat. listen for hissing noise with motor turned off but key on. if you hear hissing noise you have a hose broken or off. you will have to find it

Duane Wong

• 6826 Answers
• Posted on Jul 07, 2010

SOURCE: I have a 2001 Oldsmobile Silhouette and the front

The blower motor is either bad, or if you hear it blowing in the front but nothing comes out of the vents, then it's a vacuum motor problem. The flaps aren't angled right to allow air to come out of the vents (either for a/c, heat, or defrost).