Carl79

I recently replaced a broken heater/AC controller. Went in just fine with the help of a needle nose, tweasers and a microscope. Anyway everything appears to be working except for the air vents (dash area). I cannot get it to blow from the vents. Also.... (not sure if this is related) what actuates the fresh air kick panel vent on passangers floor? I also used the same temp cable it looked good as was operating freely, could this be the cause of my problem??? Everything else blows correctly Oh yeah !! Nothing comes out of the dash vents no matter if its swithched to vent or air conditioning.
Thanks
Carl79

Aggitated Monkey

There is a valve located behind the glove box that ports vacuum. This valve is controlled by the temp slide cable. If you remove the glove box you will see the valve and if you move the temp slide on your controller you will be able to see if it is in rig. The adjustment for the slide is located in the left consol access. You can set the slide to full cold and adjust the cable until the lever on the valve fully presses the valves plunger.

If that is not the problem then you have a vacuum supply problem. Take a good look and the 3 vacuum lines going through the right side firewall.

Carl79

Great !!! Its Saturday and agreat oppurtunity to do this. I'll look at right away. Bye any chance do you happen to know what the little rotory **** is for? Its located UNDER the glove box and it appears to be in the passenger air duct?

Vette80regon

My 1980 has this exact problem (no air from dash vents AND no front/windshield defrost air). The fan blows strong and the heat by the feet atrea is great but no defrost/front dash air....


ttt

Aggitated Monkey

You most likely have the same problem as Carl79. I'm not sure what the wheel that Carl79 has mentioned is in the vent or if it even has a function.

Another common problem is the small vacuum selector port valve that attaches to the control unit in the center consol. This vacuum selector has a plastic rivet that holds the 2 halves together and becomes weak allowing it to leak. I have repaired them by replacing the plastic rivet with a screw. I just performed that repair on my ’80 by using a large, short self tapping screw. If you were to do this you will see that the repair is obvious. When I have put the selector port valve together I also lube it with a small amount of Vaseline or similar lube.

I see that Carl79 is going to make the rig adjustment on his control cable. It doesn’t take long to do.

Carl79

Hey Fat Cat,
Thanks for the tip !...I got the valve to open and close properly however I still have the same problem...no air to the dash vents. So now I'm thinking vacuum ...but dont know how to test for it.
Where does the vacuum line from the heater/air controler go to? What should I be looking for and how big of a job is it. Thanks for taking the time to respond, I appreciate it. PS...That round dial/**** under the glove box....I think its the timer for the courtesy lights.
Thanks,
Carl79......Ps again, On my old controller I needed to wait a few minutes before the vents would activate.

Aggitated Monkey

The 1/8" vac lines (3) going through the firewall is where you want to look. One is the vac supply the second is the heat vac servo in the hose in the engine bay and the other goes to the servo that opens and closes the out side vent in the right kick panel. If you are not getting vac to the system it is mostly the supply line that comes from a "T" on the left side of the engine bay, crosses over to the right and passes though the groment. Many times they become brittle from heat and crack. Often the crack is at the groment. You can pull the old line out of the groment and slide in a new one. It dosent slid easy from the groment at first howerver it will slide out/in.

You could use a vac tester to see if you servos operate. Disconect one at a time; conect to the tester and apply vacumme. The vent servo should move. You can do this to each of them.

Hope that helps...

Stoge

I do to... just never knew what to look for. Guess I've got a project for my day off tomorrow. Thanks for the tip!

Jfostercorvette

Yes, I know this is an old post. A very old post. i am looking for a little help. I have an 1980 Corvette. A/C works and works well however, the cold air comes out the heater ducts and not out the dash vents. Here is what I have done in accordance with the previous information in this post.

1. Made sure the cable was adjusted to hit the plunger behind the glove box.
2. Installed a new vacuum port switch from wilcox that they modified to ensure it sealed.

What happens is I turn on the A/C, compressor turns on cold air comes out the lower vents. I turn the car off I hear hissing at the A/C control. I assume that means I have vacuum which seem to me I do not have a vacuum supply problem?

Not sure what to do next? I did look at the vacuum lines going into the cabin but they seem ok no visible cracking or other damage.

Thanks in advance for your help

billschroeder5842

I'm thinking that you need to test the servos. Also, for a 80, your hoses maybe a weak and not able to hold vacuum. I recently did a heat core exchange on my 82 and put in all new hoses- it is like a different car.

Attached is a diagram. My guess is your problem is somewhere between your 3,4 port.

DUB

YES...if you are getting a 'hissing' sound that is actually GOOD...so you know you actually are gettign vacuum to the vacuum switch that you attached to the backside of your control head.

When I run into this issue I will have either my vacuum pump on and supplying the vacuum to the system so I do not have to have the engine running. YES..I used to do ti with the engine running and is 'do-able'. I will actually remove the vacuum switch on the control head and manually move it and see if I can get the doors to operate and direct the air. This allows me to be able to put my ear to this switch and listen for vacuum leaks., Then I attach it and test it again. Often times the switch may leak vacuum....but a slight bit of movement in either direction can get it to stop.

DUB

IvanoMan

Thank you for your shema, I'm actually having the same problem.
Air sysem is running but no air come out.
Can you tell me where is the main air entrance ?

Slick1966

I have a 79 the AC is fully charged I can move the control over and the heat will come out move it back to the white and it's the vent but move it to the cold and the cold air will not come out I have tried pushing the plunger behind the glove compartment in with my finger but no air comes out but I have not tried to adjust the cable yet do you think this might work if I pull the cable and make it apply the plunger but I figured it would be the same thing by doing it with my finger I push the plunger with my finger all the way in and no cold air came out but does the cable matter?

C6-CYa

FYI, it's never good to open a really old thread, as people start to read though all the posts and suddenly realize they are reading ancient stuff and stop reading.

Always better to start your own thread where you will get exactly what you need. Add this post as a link if you want.

eboggs_jkvl

Necro thread of 15 years.