I just bought a 96 S-10 Blazer.

The air conditioning/heat will only come out of the defrost vent on top of the dash. And, when I turn off the truck after running the AC it hisses. Vacuum leak I assume.

I found the vacuum "ball" connected to the hood and the line is dangling from it.

I also found what I think is the "T" it is supposed to connect into, but it is connected elsewhere. Is it possible the previous owners re-routed the vacuum line, and would there be a reason?

I don't think I want to disconnect the current line and connect the one that is supposed to be there... Not sure what else it could be connected to or what problem that might cause.

Thoughts? Solution?

 

the vacuum that controls all your selections for heat inside the cab should just be solid vacuum, usually theres a line going into the fire wall near the passenger side. just look for a hard plastic line or small rubber line going into the cab and run your own line if you cant find the original one

 

I had a vacuum problem with my 4x4. I researched and put together a doc from several sources. It is attached. I used a Mity-Vac to measure the vacuum as I troubleshot the problem. A cheap vacuum gage will work also. Since yours has been hacked, you can follow the diagrams to correctly route your lines. Spray Simple Green to help find the leak. I started at engine vacuum and tested each line out from there. The orb stores vacuum to operate the system when there is low vacuum (when the throttle is pressed hard) and there is a demand on the system. Your cruise control also operates off vacuum. The controls inside will hiss when the vacuum is released or when the switch is operated. Verify you have vacuum at the hard line going into the firewall before you tear the dash apart. Your main problem is probably a vacuum hose with a hole in it or possibly your hacker inverted the vacuum check valves. If yours is a 2WD, you don't have to worry about the number 1 cause of S10 vacuum problems. HTH