Hi everyone, This is my first post on the forum hopefully someone will be able to help me. I have a 1997 Blazer Lt 4x4 4.3l with 188k miles on it.

My problem is my AC will only blow out of the floor and the defrost vents. I can't get anything out of the front vents. Here's a list of what I checked and fixed so far.

1.Checked the vacuum lines under the hood. All of the checked good and after replacing the PCV valve I got a good vacuum at the vacuum canister.

2. I located the vacuum lines under the glove box, one orange line and one grey line. Orange line was good but the grey line was disconnected. Reconnected and this allowed me to switch from floor to defrost now (it wouldn't work before only had defrost) but still no front vent.

3. 4WD works in all positions 2hi, 4hi, and 4lo.

4. I pulled the control module out and checked for vacuum there and it had it coming from the grey line. All heat and AC controls work, Fan works from low to high, and temp controls work between hot and cold.

What's my next step?

Do I need to check the control module and make sure it's routing the vacuum correctly? or do I have a solenoid/actuator issue?

 

Behind the glove box...does it look like this? Can't remember when they changed the layout, but my '96 is different than my '04. The pic in the link is from the '04.

Anyway, you didn't mention the other vacuum lines inside the dash. Have you checked them all? I use a MityVac; start by pulling the plug off the back of the HVAC control (the plug where the colored lines come into) and hook each one up to the MityVac. That tells me which actuators are working. Since you are getting vacuum at some of the lines, it sounds to me like you have an actuator problem. When you lose vacuum altogether, air will only come out the dash vents (the default position with no vacuum).

On my '04 Blazer, there are two actuators under the driver's side dash, just above the gas pedal (the '96 Sonoma layout is a little different). They're pretty easy to access. I suspect you've either got a bad actuator, a disconnected vacuum line, a bad mode actuator; or, you may have a broken door or flap that directs the air flow.

 

Sounds like the blend door actuator. Do you hear any groaning from behind the glove box?

 

I'm not getting any noises coming from the dash at all. I've looked under the driver side dash but I haven't been able to find the actuator at all. I have the found the floor actuator and it works properly. Does anybody know where the defrost/vent actuator is?

 

If your '97 is similar to my '96, it won't have actuators under the driver's side dash. If your HVAC is similar to my '04, then you will be able to see the actuators by removing a few of the panels near the gas pedal. Take a look at some of the pictures here and here. The first set is from my '96 Sonoma; the second set from my '04 Blazer.

 

Mine looks like the 96 in the picture. I think I'm gonna track done the blue vacuum line and make sure it's still connected. Anyone know of an easy way to get to it?

 

What I know from owning a 97 is that the floor & defrost is the default setting when there is a vacuum leak. Look under the vehicle at the lines going to the Transfer case. Mine rotten under there & the top under hood lines were OK.

 

Well...not that I know of. I had to take my dash apart and tilt it forward. Blue line goes to the actuator that opens the dash vent door flap. In the pictures, you can see that the default position (no vacuum) is the door flap is closed, so no air to the dash vents. They didn't make it real easy to get to that actuator, or the one connected to the brown line. Later models are a lot easier to look at the actuators.

 

I managed to find the actuator and found the blue line was disconnected, I reconnected it but still not working. Now when I turn the car off with the ac set on floor I hear a noise in the dash when the vacuum cuts off. I'm getting good vacuum on the line so I'm thinking I have a door or actuator problem. I'm going to take the dash apart this weekend and see what the problem is.

 

You mentioned you checked teh vacuum lines under the hood. Are you sure the 6" line by the ABS system is connected to the Vacuum canister in the fender?