1989 Corvette with a heater problem

Q. I own a 1989 Corvette with a heater problem that I can’t figure out. I changed the thermostat, and ran the car till it got hot. I then checked the heater hoses and the radiator hoses and they are both hot. I did get heat a couple of times and am thinking that a heater door is not opening. Is there a vacuum that operates this door and is there more than one ie; one under the hood and one under the dash? Is there anything else that can be causing this problem besides a plugged heater core which I do not think it is as all the hoses are hot? Thanks, Roger

A. Roger: That depends on which style of HVAC it has. If it is auto temp then it uses vacuum to control the motors that open and close the blend doors. But if it is manual AC then it uses basic cables.

But that presumes the coolant is hot enough and that it is flowing through the hoses and heater core with enough force. You say the hoses are hot but how hot is hot? We would use an infrared thermometer to measure actual temperature and be looking for a minimum of about 160 degrees on the hot hose (you will not be able to touch a hose that hot) and about 15% to 20% less on the return hose. The return hose is cooler because it drops heat into the air circulating through the heater core.

Another item that can upset some of the automatic HVAC systems is the outside temperature sensor. If the outside temperature reading is wrong you may not have heat or you may not have AC. In your case I wouldn’t be surprised if you find a clogged heater core that needs to be flushed.

Originally posted on National Corvette Owner’s Association newsletter http://www.nationalcorvetteowners.com/


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