I got an 84 vette and the heater blows air and the air conditioning works but the heater blows cold. I have heard that there is a valve in the engine compartment somwhere that i would need to turn to get the water flowing to heat up the air. if any one has any comment please tell me

 

It should be in the line hose that runs from the block or water pump to the firewall on the passenger side. it will have either a wire or vacuum hose attached to it with a diaphragm actuated lever that opens and closes the valve. it will be located high on the firewall along sine the blower motor. hope this helps. also you may want to make sure the cooling system is full. I have this same problem on my '87 and I believe it is because I cannot get the air out of my cooling system. It was not working at all but I replaced some of the air with coolant and now it works sometimes. I think if all the air was out it would work fine. good luck with this problem. Cheers

 

The valve might be the problem, but also you have blend door actuator that contols the blend of cold air and hot air form evaporator and heater core if the valve doesn't cure your problem. [8D]

 

In our car, our Heater Control Valve (which I believe is the valve you all are referring to) is shot according to my mechanic. Our car does the exact same thing mentioned here...

I have not been able to find that part here locally, new... does anyone have any clues on that? I am in Canada... could I order it fromDelco or something in the States and have it delivered?

Anyways, that's secondary... for our car, my mechanic (who walks on water, in my books) did a neat little trick to get us through the short-term. He attached a very very small spring from the Heater Control Valve to the wheel well, thus providing just a little bit of tension to act against the vacuum. I believe in our car, it's the internal diaphram that's worn out somewhat... anyways, this trick has worked for a couple months now for us. It's not a permanent or proper fix, by any means, but it has at least gotten some heat into the cabin for us....