Hi there all of you.
I´m new here on this forum.

A small and quick presentation.
Swedish
2 Corvettes, 2005 conv base. 72 conv base.

My question is about the c3.
How does the heatersystem really works?
What i mean is what is happening really behind the dash.
It´s an ac car.

For instance:
The heater control valve are closed in max/ac position but open in all the other positions on the heater control.
What is it then that really adjust the heat in to the coupe?

I´m planning to do something about the fact that it comes heat in to the coupe even when i have set the heat adjustment on the heater control to zero. I going to take out the heater box from the car and renovate it.

So i need all information that i can get, if possibly even some kind of instruction or schematic on this.

Please forgive me for my sometimes bad english, i do my best.

Regards / Anders

 

Hi Anders,
WELCOME!!!
I'm glad you've found Corvette Forum.
The heater/ air conditioning system is quite complicated so I'll ask if you have any books to help you with information?
If not, you should consider buying the 1972 ASSEMBLY INSTRUCTION MANUAL, (AIM), and the GM 1972 CHASSIS SERVICE MANUAL for your 72.
These will have lots of information and schematic drawings for your a/c system. They are available from many of the larger venders on this site. Both will be a BIG help to you.
Right now I can't help with your a/c-heat situation because I don't know much about cars with a/c., BUT, I'm sure some other members will reply and offer some help.
Good Luck!
Regards,
Alan

 

The change in temperature of the heater/ac system is accomplished by a blend door. All the air is forced through the ac evaporator whether the ac is on or not. The air is then either guided through or around the heater core or a combination of the two to get the different temperatures. The temperature control actually opens or closes the blend door to the heater core. There are many sources of unwanted heat that can enter the system, one of them is the water shut off valve malfunctioning(vacuum operated). Another cause is the seal at the rear of the hood, if it's not there, then engine compartment heat is allowed to enter the cowl area where the heater blower draws in air.

 

Thank you for your answers.
The result is more questions.
Please have patience with me.

Where is the blend door located? I suppose i have to remove the heater box to be able to find out if that one is leaking?

The air is forced through the ac evaporator you say but where does it come in?

Where is the water shut off valve located?

Do i separate the ac unit from the firewall in the engine compartment just by remove the condensator with it´s box? Is it then "free" so to say to take out the heater box the normal way?

How do everything else work? For instance i´m talking about the vacum that operates all the vent ducts and so on.

Regards / Anders

 

Hio Anders,
I can't imagine getting into the heater/ac systems with out the AIM and Chassis Service Manual. Honest!
Regards,
Alan

 

Anders: follow Alan's advice. Order the AIM and the service manual before you undertake the project.

 

This may help

http://www.corvetteforum.net/c3/juli...tCore_orig.htm

http://www.corvettefaq.com/c3/heatercore.html

 

Hi there all of you.

Thanks for the answers, most helpful.
I have now bought the AIM, it´s as helpful as you said. Thanks.

The corvette is now sleaping, the winter is here so i can´t drive it for at least five month´s.

Back to buissnes:
I´m now going to start to remove the part of the heater system that is located inside the coupe. It´s an ac car so i belive that it´s not neccesary to remove the ac unit in the engine compartment to solve the problem with heat leaking in to the coupe ( i hope).
But i havent really figured out about the heater core. Do i remove this one (if neccesary) from the engine compartment even on a ac car? And can i then do that without remove the ac unit?

I´m planning to buy and replace all the seals in and around the housing. Is it recomended to replace anything else when i have it out?
I mean anything else around this area under the dash, for example wiring, contacts, vacum details both in this system and maby in the wiper or the lighting system, etc etc? It should be good to avoid to remove it gain.

Please forgive me for my sometimes bad english.

Thanks.

 

I had a lot of heat coming in even with the heater turned off. I would make sure the shut off valve is working before taking everything else apart. On the right wheelwell under the hood is a vacuum operated shut off valve in the heater hose line. My problem is that my engine doesn't provide enough vacuum to operate it due to the engine cam I have. I installed manual shut off brass ball valves in both heater hose lines, only one will do but I did both. After installing the shut off valves, I do not have any more unwanted heat coming into the cabin. Here's a picture where you can see the 2 shut off valves with red handles I installed in the heater hose lines.

 

Hallo Mike and thanks for the answer.

I already have a manual operated shut off valve on the heater hose line.

So i think i can say that´s not the problem.
When i shut it of no heat is coming in to the coupe.

The problem accours if i dont shut it off when the weather is warm on the day after i have had it open the evening before when i needed some heat in to the car.
So i do think that the problem is that the seals in the heater assembly has gon bad and the air is leaking in to the coupe through the hater assembly even if it closed so to say.

Mayby i´m wrong now but i think the 72 don´t have that vacum shut off valve so when the seals in the heater assembly goes bad this problem will be a fact. So therefore many owners of a 72 have installed a manual shut off valve to prevent that problem.

By the way, how do i remove the instrument cluster in the middle?

Thank you very much, nice to heare from you.

 

I believe that if you have hot coolant flowing through the heater core with no shut off valve stopping that flow, no matter what you do, including installing new seals in the heater box, you will still have heat coming into the cabin. If you do not want to shut off the valve by hand under the hood, you can add a vacuum operated valve or install one that uses a cable from inside the cabin to open and close the valve.

I took my complete heat/ ac box apart, installed all new seals, and thermal insulated the box inside and out. And I still had heat coming in when the shut off valve was open and all heater controls turned off.

Not sure how your 72' console comes apart, my 80' is different. The AIM that you purchased should show you how it's assembled. On my 80' you have to remove the carpet panels on the sides of the center console to get to the console screws underneath.

 

Hallo Mike.
Thank you for the answer.

I think you are correct about this as far as i can understand it.

I think i will give it a try anywhay.
I think i might get rid of some of the incoming hot air even from the engine compartment it self.

I have read somewhere about a solution to put in a vacum operated shut off valve that works automaticaly.
I must search for it.

Regards: Anders