Troubleshooting ventilation
Thread Starter
Heel & Toe
Joined: Nov 2008
Posts: 24
Likes: 0
Troubleshooting ventilation
I have been trying to get the air flowing through the vents like it's suppose to. When I move the selector from defrost to heat to vent, I can hear a hissing sound from the switch like a vacuum leak. The air comes through the bottom most of the time. Sometimes it will come through the defrost vent, and will barely come out the vents. I replaced the defrost actuator looking part that is mounted under the drivers side of the dash. Everything worked for a while, but is now spiratic. I tested the same looking part behind the passenger side kick panel, and it seems to be working. It reacts like it's not to be getting any vacuum. I am considering replacing the heater control vacuum switch. There looks to be 4 small vacuum lines going into it. I have a vacuum diagram for it. From what I can see on the diagram, this system has 4 or 5 valves or more. I have replaced the heater control valve, and it works fine. Any help will be appreciated. Thank you...
Melting Slicks
Joined: Apr 2008
Posts: 2,623
Likes: 242
From: Russell Ontario
St. Jude Donor '09
There is a nut or screw behind the control switch make sure it's tight .But don't over do it it's plastic, if that does not work take it apart and change the "o" ring , or check for a broken vaccum hose or a bad connection , mine did that for a while and I just snugged the screw on the back and it works fine!! Ron
Let me know how you make out!
Let me know how you make out!
Thread Starter
Heel & Toe
Joined: Nov 2008
Posts: 24
Likes: 0
That sounds like a good idea. If I replace the o-ring, I hope it can be done without taking out the entire control unit. I will let you know how it works. Thank you for your help. I'm sure I will need more help. T.R.
Melting Slicks
Joined: Apr 2008
Posts: 2,623
Likes: 242
From: Russell Ontario
St. Jude Donor '09
I think you can do it without taking it out but you need to be careful it's tight , why don't you try and tighten it first ,it may save you time , there was a article on this on another site I'll try and find it for you !
Ron
Ron
Melting Slicks
Joined: Apr 2008
Posts: 2,623
Likes: 242
From: Russell Ontario
St. Jude Donor '09
I think you can do it without taking it out but you need to be careful it's tight , why don't you try and tighten it first ,it may save you time , there was a article on this on another site I'll try and find it for you !
Ron
Ron
Thread Starter
Heel & Toe
Joined: Nov 2008
Posts: 24
Likes: 0
After taking off the heater control vacuum switch and cleaning it, it works good. I vacuum tested the plenum valve located on the top of the passenger side, and it checks ok. It looks like it is hidden under a screen just under the passenger side wiper arm. Hopefully that will never have to be changed. It looks like a major project. The inside air valve located behind the passenger side kick panel checked ok, but can't see it moving when operating the controls. Do you know what the function is of the inside air valve, and when it should move? The air comes out the correct places when it suppose to now, so not sure about that valve. Thanks for the help Ron. You saved me a lot of time and frustration. T.R.
Melting Slicks
Joined: Apr 2008
Posts: 2,623
Likes: 242
From: Russell Ontario
St. Jude Donor '09
I think mine was the same I had the kick panel off when I redid my carpets and I could not get it to move it may have somthing to do with tha A/C in the car! or the fesh air intake! Sorry I could not find the article about the switch , but it sounds like you fixed it ! Ron
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
The Chevrolet Chassis Service Manual and the Assembly Instruction Manual (A.I.M.) have the logic diagram for the A/C/heater control head function. You need that to know what dampers are supposed to function with each control position setting. I think the best way to evaluate everything is to disassemble lower console far enough to get at the control head. Then remove each "feed" line (one at a time) from the manifold and suck on the line to see if the connected diaphragm moves (it should also be the correct diaphragm as per the logic chart). Once you know that all of the servos are working properly, you can hook the hoses back to their normal positions on the manifold, start the car and check out that the control head is working correctly in all positions also. That should solve your problem.
I'm not positive about this, but I think that there may be a seal of some sort in that (circular) vacuum manifold on the control head. You might want to check up on that and be sure that the seal is in good condition (not flattened/hardened from years of service) before you button it all back up.
I'm not positive about this, but I think that there may be a seal of some sort in that (circular) vacuum manifold on the control head. You might want to check up on that and be sure that the seal is in good condition (not flattened/hardened from years of service) before you button it all back up.
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