1998 Ford F-150

Heater blowing cool air, where would I find the heater control valve to check it and/or replace it if it is faulty? Any other hints?

July 24, 2006.

I dont think your truck has a heater control valve. The radiator fluid should always flow thru your heater core in your car. The temperature is controlled by the temperature blend door. The situate the heater core and close the door over it allowing air to flow thru the evaporatoe and into the ducting. When you select heat, the door opens allowing some air to flow across the heater core and into the ducts. The more the door opens, the more air is directed across your heater core.
If you are not getting warm air with full hot selected, it sounds like that door is not opening. Other possiblities are clogged heater core, bad electronic control going to the actuator for the temp door.
In looking at the electrical control circuit, it is very simple. There is a dedicated fuse for the Blend Door acturator in the junction box fuse/relay panel that delivers power to the actuator. It had a ground wire that goes to G200 ground. Three other wire go to the temp control switch. If youdisconnect the plug to the hot/cold control knob, and jumper pin 1 and 2 together, that should drive the actuator to full warm. Short pin 2 to 3 will drive it full cold. Test it out and see if the mortor will drive. If yes, replace the control switch. If not, check for power to the motor and a good ground. Powere and ground at the actuator, and still no movement. Replace actuator.
Good luckl.

Jul 24, 2006.