LAPII

67 SBC w/factory A/C...when heat engaged blowing cold air? What do I check?

Frankie the Fink

Check radiator thermostat and heater control valve and then routing of heater hoses to make sure flow is correct.... Sometimes owner's will bypass a leaky heater core...

Jud Chapin

You don't say whether it's a/c cold air or out side temp cold air. First thing I'd check is coolant level.

midyear

First check and see if heater hoses are getting warm, AC cars use a heater control valve that could be stopping the flow of coolant through the heater core.

StingU2

... A very good chance it's the heater control valve, the valve acts much like a thermostat in the way it regulates the amount of heat produced by the heater for fluid to flow through the heater core. If not for the heater core valve in a A/C car, the vehicle's heater would be in a continuous state of warming the passenger compartment. This affects the efficiency of the air conditioning as the cold air is competing with the warm air in the attempt to exit the vehicle's heating, and cooling vents.

-Bruce

SI67

Do you mean that you are getting cooled air, or just air that hasn't been heated? If you are actually getting COOLED air, have you looked to see whether or not your A/C compressor clutch is engaged all the time, even when A/C **** is pushed all the way in? I suspect that it's really just unheated air, and that the folks pointing to the heater control valve are right on the money.

By the way, I would suggest that in the future, you might want to give a somewhat more descriptive title. That way, folks who are well-informed on the subject will see it and folks who are not all that familiar with topic know that it's a thread they might want to skip over.

LAPII

It's just blows air....not cold....but not heated...is there a way to test valve? Or they just go bad? SI67 got it on title? Thanks.

StingU2

To test the valve... with your car running, the vacuum line running from the heater core to the heater controll valve should be warm to the touch. If it is not warm, then the control valve may possibly be stuck in place, and you should put in a new one. They run around $30-$40, unless you prefere a correct repro one which will cost you around $100.

-Bruce