I have looked through the boards and really haven't found the issue that I am having.

Maybe somebody can help with troubleshooting. Here goes....

The sysmptom is no hot air when the heat switch is in max position. AC works fine. Normal operating engine temp is good between 195-210. Checked coolant level and it is good. No dampness in passenger floor after engine running for some time. No hiss sound from heater controls. No leaks from heater control valve. Removed vacuum tube from control valve and no change. Changing the heater controls sounds like the air flow doors are operating. The Defrost, Heat, and Vent controls work properly. The fan has plenty of air flow.

I have read some about checking the temp of the hoses that are located from the control valve to the firewall and from the control valve to the manifold. I didn't understand what the temps would be on each hose if the valve is working and the core is not plugged.

Any ideas or other things to check would be helpful.

 

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If the heater lines are cooler then the radiator hoses, then bypass the diverter valve. If the lines are still cooler then it's the heater core.

 

Sounds like either a plugged heater core, bad control valve or vacuum to the valve, or the cable has come loose from the blend door. I would 1st check the control valve, look for leaks then check for vacuum to it and also check it with a vacuum tester and make sure it holds vacuum when applied with the gauge. If all thats good then remove the pass. side lower dash cover and make sure that the heater cable is attached to the blend door and that it works smoothly. If that is good then it leaves the heater core being plugged up.