Heater box

[brew]

Hi everyone. I have a 79 vet that has a heater problem. The defroster does not work, I can not get any air to the defroster. The blower works great , I get plenty of heat a my feet but none up top. I have not had any thing apart in the inside of the car.
Is the door in the box vaccuum operated?? How do you get in to the box to work???
This is my first Vet so I'm a little lost.

Thanks for the Help..

 

[78SilvAnniv]

Welcome brew!

Welcome to Corvette Action Center.
My husband replaced my heater core this past October and I'll have to ask him how he accessed the area and if he knows what to do for a non-working defroster.
You may wish to search posts/threads by bobchad, since I think he has done some similar work. You could also perform a search with key words:
heater
heater core
defroster

Heidi

 

[Bob Chadwick]

This is most likely a vacuum issue, either a leak or a bad actuator or control on the dashboard.

There is a vacuum source that comes into the heater control and goes out to the actuator on the left side of the center of the air distributor. When you move the slide from vent to heater to defroster the air is supposed to move to the appropriate selection.

Check the vacuum diagram on this page http://home.attbi.com/~jchadwick/ventilation.htm prepared by Vmrod here at the CAC for the routing. A quick look suggests that a black vacuum line comes into the bottom back of the control and goes out to the actuator as a black/blue line.

The first thing I would do would be to check to make sure you have vacuum at the various points in the system. With the engine running I would put a vacuum gauge on the end of the black/blue line that attaches to the actuator and see if you get vacuum as you work the control. If you do it would appear to be a bad actuator that might free up with some WD-40 or might have to be replaced. If not, I would pull the black line from the control and see if you have vacuum there.

Evidently the control can go bad as well. Mine will go to all three settings but only if on the first attempt I take it all the way to the right and then come back to the left to the a/c setting and then back to where I want it set. The way it has been explained to me is that there are some pieces within the control that can break with age and cause this behavior. I will be replacing mine as part of the insulating that I am doing to my car at this point.

Let me know if I can be of any more help.

Bob

 

[Doc Rebuild]

C3 Climate Control

Sir

This is a very common problem on C3 Corvettes. I wrote Tech Tips about solving this shown below. If you have a 1979 with AC you can see the hose routing in Full Color below. If you have an early 1979 without AC (before it became standard equipment) you can see those hoses and the routing in Full Color also below.

Geoffrey Coenen
NCRS #2473
NCM Lifetime #105
Precision Valley Corvette Museum Charter Member #20 (I think)
Vettehead #18-1
Retired #1 56, 63, 67, 68, 68, 69, 75, 99 and I want more!
,
Tech Tips
1979 AC Climate Control Vacuum Hoses
1979 Heater Climate Control Hoses

 

[Vetsvette2002]

Welcome in Doc.
Your knowledge and expertise is always refreshingly accurate and I know you talk straight.
Don

 

[brew]

I am on the way

Thank you all I have narrowed it donw to a lack of vacuum. I will have to order a new vacuum line kit and I do be leave that may take care of the problem. I just got the car I don't know how many owners she has had but I may be the first one to do any thing to the Vet for a long time. Most all the hoses and belts, every thing is in poor shape. Many parts missing, the sealing for the radiator and intake for the twin snorkel intake air cleaner is gone. The radiator leaks at both inlet and outlet. Front oil seal leaks, trans has a leak, and on hard acceleration the rear end makes a sound like disc brakes trying to hold back an engine being torqued up. But I am working on it slow. It does run and I do drive it. Out side appearance is very good. New seat covers and carpet. I think that most evry thing is a labor of love on a Vet. The engine and trans come out this spring for some freshening up, and may be a little more power. Any ideas what would be a good engine for just cruseing??? I enjoy a winding road and taking trips.
Thanks again.
Del