93 s-10 Blazer, Air only blows from defrost vents at top. I assume this works off vacuum? Can anybody confirm that and where is that vacuum line on the engine?

 

Theres a Vacuum tree that connects to the backside passenger side on the Plenum. Theres about 2-3 lines going into a single tree and then that tree connects to a nipple sticking out from the upper plenum. Its close to the Dist. You might have a vacuum line dis-connected or broken. I was having the same problem and I realized that I didnt re-connect it the one time I had the plenum off.

 

Yeah I see it. Its connected but it doesn't appear to be making a good seal though. Thanks for the help.

 

Then maybe you have a break in the line somewhere else.

Theres also a type of distributor thats behind the vent controls and it connects to the vacuum lines. That when you move your lever up and down for the different settings it opens and closes the vent doors. Theres a chance that could be bad.

Check the vacuum lines first before taking the dash apart.

 

Thanks for your help 94BlazerPA. The problem was right where you said. There is a check valve coming off the nipple that sticks out of the back of the plenum. It was cracked preventing a vacuum. $2.99 and my vents are now working and as a bonus it fixed my cruise control. I had no idea the cruise worked off the vacuum.

 

Yeah same here, my Cruise control was out as well, i didnt figure it was coming from that. That vacuum tree controls alot. Glad I could help.