I have a 95 Z28 that isn't blowing air out of the dash vents. Air blows thru the defrost,and the floor vents. The air isn't hot, but will warm up. Any ideals on what I need to look into to get the air movement into the vents would be greatly appreciated. Blend door is operating. Thanks

 

No "ideals".... but a few "ideas".....

The air distribution is controlled by various flapper doors that are powered by engine vacuum. The ususal problem is a broken vacuum check valve near the engine.

Courtesy of Shoebox:

http://shbox.com/1/hvac_vacuum.jpg

http://shbox.com/1/vac_check_valve.jpg

If you notice in the diagram, only the flapper door that switches between heat and AC is powered by a cable, off the temperature ****. If you don't feel the air switching from hot to cold when you turn the temperature ****, it may be a problem with the cable.

 

Thanks, I'll try the check valve.

 

Sounds like the check valve to me. I believe when there is no vacuum it'll default to the defrost and floor......Id say the check valve or one of the vacuum hoses is the culprit....The check valve is near the PCM on the passenger side engine bay

 

Plus...

http://shbox.com/1/4th_gen_tech2.html#HVAC_vacuum

 

Thanks everyone. I put a new vacuum check valve in, didn't change anything. I'll check the vacuum lines next.

 

I had the same problem, but on the passenger side, there is a T shaped fitting with 3 hoses going to it, and mine was busted... I replaced with what looked to be the same thing at a autozone, and it worked.

But my cable is also screwed up, so I have no heat at the moment... And the perfect time to, right in the middle of winter.... And my compresser seals are shot, so I'm screwed in the summer to. Lol.

 

Also, just in case anyon else is having problem with th cable. It's like $40 from gm.

I tried fixing it, but I couldn't get the cable back on the track.

 

It would have been a good idea to do some testing before replacing anything (though, I know the valve is cheap). The next most common leak point is the hose to the vacuum tank.

 

I left mine blowing on the floor and now that's all it will do. When I turn the **** it just hisses like it's trying to change but can't. I'll have to check out those lines. It does get warm though.

 

Well I changed that valve and I still have the problem. I think the leak is where the line hooks to the control. I can still hear it hissing there.

 

The "T shaped fitting with 3 hoses going to it" would be the vacuum check valve. Look at Shoebox's links.

As Rob/Shoebox noted, test before you assume. Check the line all the way from the manifold to the check valve, to the vacuum reservoir, and to the dash panel. If you have a hand vacuum pump, use it so see if you can pull a vacuum on the system. Could be a broken elbow, cracked hose, a connector that fell off, etc.

 

Finally got back on my vent issue. Checked all the vacuum lines going to the check valve. The hose going to the manifold from the check valve was broke in half. Thanks for all your help. Works great.