Questions and Answers

Ford Has No Heat

Q. I just purchased a 1991 Ford Crown Victoria with a 5.8 liter engine. It has an automatic transmission, A/C, cruise control, power windows, door locks, and seats. I am not sure if it has ABS or not. My problem is the heater. I cannot seem to get anything but warm air. I have changed the thermostat, changed the radiator cap, swapped the heater hoses on the heater core, checked the heater core to be sure it was not stopped up with no improvement. The vacuum modules all seem to be operating properly. Any advice or help with this problem would be greatly appreciated.

A. I would look at the heater control valve. It sits in the heater line going into the heater core. That is the most likely problem. They have a tendency to get stuck in the closed position over the summer. First thing to do before you condemn the valve is to make sure it is getting vacuum. Pull the vacuum line off and have someone switch the temp from cold to hot and back. You should feel vacuum in the line. If you feel it, then replace the valve. If there is no vacuum, then you need to make sure there is vacuum going into the heater panel. You'll see a vacuum line going through the firewall. Check for vacuum there. If you have it there, then you need to pop off the front of the heater control panel and make sure the vacuum switch is working.

It is possible the heater core is partially clogged up. There is no reliable way to check it. It is assumed that if everything else is good, then it's the heater core.