MrMagic

What happened; you guys just dropped off on this. I have the exact same problem on my 81. Everything on the system works but it will not blow hot air. Air flows thru the proper vents but its never hot.
I removed the glove box and watch the temperature control switch move and open the door. When the cable moves the switch to the cold position, it does depress the vacuum switch like it is suppose to. I'm wondering if my correction is my problem. My car wasn't blowing A/C air out of the vent registries on the dash. I found a vacuum leak on my intake manifold and connected the line and my A/c started blowing out of the registry again. I notice that the originator of the post here said that he just connected his A/C and defrost system. Could it be something there.

xkeots

Hi,

For now I managed to get the heat and defrost working and I know that it is the replacement switch that I bought that is now allowing the vacuum for the A/C to work.
For heat on the 77 I had to replace 2 switches. One on top of the vent behind the passengers side dash, with 2 vacuum lines, with a spring loaded switch, that when you move the bottom cold- hot lever it pushes that switch on and off. One of the vacuum lines goes to a control in the engine compartment between the hot water (anti-freeze) to the heater core. It makes the hot water flow or not. If you move the lever for cold to hot the when it is on hot feel both hoses on each side of the control on the passengers side. The one going to it will be hot as soon as the motor warms up. If the switch is working, the side going to the core will be hot too. If not do what I did, replace both as they are not too much money.
I will fix the A/C in the spring. It is the new plug in behind the main switch with he 5 vacuum lines. I am happy to have cool & Hot air out of my lower ducts and defrost in the winter. I do not need A/C in this blizzard that we just got.
I have found that some of the new re produced parts really suck. I had to make a few good parts from a new and old part.
Good Luck
Jack
77 C3

xkeots

I found that on the new part, the spring was too heavy for the lever and cable to push the white cap in to make the vacuum work. I had to use the original spring, which was lighter and old cap on the new body and internal nail.

Thanks
Jack

MrMagic

I think i know the switch you guys are talking about. It resides at the end of the stroke when you move the temperature cable to cold. there is a little tab that pushes the switch in when the cable moves all the way to cold. I thought that may be my problem but wonder about this: - isn't the car design so that if you move the cable between hot and cold, you are suppose to receive a mixture of cold air and hot air (warm)? I don't see how you could ever get warm air if the only way to get the hot air to flow is to depress the switch with the temp cable being in the absolute cold position. However, I did manually hold the switch in just to see if the air would blow hot and it didn't. I guess my problem is something else!

tommyleea

Maybe your thermostat is stuck open.

MrMagic

I don't think its the thermostat. If it was, there would be some hint of warming. My air is as cold as a/c air. I think its my water shut off valve under the hood. I don't think its opening to allow hot water in. I was going to change it a couple of days ago but my Opti Spark died and took precedence. Once I get it running again, I will change the water valve and let you guys know how it turned out!

MrMagic

That was it! There is a water temperature control valve (or I have heard others say Heater Control Valve) under the hood on the passenger fender well. Heater hose goes to it before it enters the car. I change that and I'm as warm as can be!

flaco1801

take the blower resistor out and u can see if the temp door is opening and closing...