I have a 97 Blazer and I'm having issues with the vents. I'm only getting air out of the front defroster and floor vents and I get nothing out of the middle ones. I have complete control over the speed and temperature (The cold is just regular air and not AC cold but i feel its because its stuck on a certain vent setting or it just needs to be recharged).

Just wondering if anyone had any thoughts on what could be the issue with it. I did at one point think that it had something to do with the vacuum system as when i picked up the vehicle last winter it had a random vacuum hose that wasn't attached to anything between the ball thing on my hood and the first T connection. I removed the random T off as I couldn't find anything it would connect to and it got my 4x4 to engage again (which was the problem I was looking to fix at the time). Any places to start looking would be a great help, thanks for your time.

 

Its a vacuum issue. Manu, many discussions here, but basically you have vacuum lines going 3 places - the vacuum reservoir, the transfer case, and the HVAC system. Hence, the various tees. Search around a bit, you'll find vacuum diagrams and pics.

 

Yea I printed one off from here and tried to go through the whole system to see if anything was wrong or missing. This is the diagram i used:



When I look under my hood i see the reservoir, from there a short line goes to T and that T splits into one line that goes to the transfer case and another line that goes to the engine. That's all I could find and according to that diagram it should T off to the cruise control (Which works perfect) and T off to the Heater/AC Controls. Where do the vacuum lines connect to on the Cruise Control and Heating/AC Controls? If I am able to locate those I could work backwards and see what the problem is, but as of now i just have no clue where to be looking.

 

That's an older diagram; no vacuum anymore for the cruise control. Scroll through here; toward the bottom is a picture of the vacuum lines under the hood.

 

Ah that makes sense, I remember hearing that a while back. I took a look at that picture and compared it to my setup and definitely don't have that line going down to the HVAC controls. Where does that HVAC line run to after its split off of the transfer case line? I took a look and felt back against the firewall but couldn't locate the place where it connects to.

 

there are little vacuum lines that are attached to the back of your heater controls that control the vents. if those lines popped off or broke you should hear a hissing noise. put your ear up the the heater controls while its running and switch the vent settings and listen for hissing. if it hisses at a particular setting and wont stop then the seal in the switch is bad. there should be a little black hose about a 1/8 of a inch thick and may be mistaken for a wire behind the engine going into the firewall. thats your heater control feed line for vacuum. sometimes they brake off right at the firewall.

 

It's kind of hard to see, partly because it splits off into a hard plastic, smaller diameter vacuum line. But it should be in that mess of wires that goes through the firewall on the driver's side corner.

 

Found it! It was under all those wires just like you said, went to the store got some new line and a T plugged it in and BAM all my vents work. I'm soooo glad it was just something small and I didn't have to start mucking around behind the dash. Thanks for all your help. The total repair cost was about $1.50 for the T and $5 for the vac line, funny how such a small thing messed all that up.

 

Glad you got it sorted out.