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Q: Heater not working.. on 1998 Ford Expedition

I just bought this 98 Expedition and the heater is blowing cold, just replaced thermostat, and I am trying to figure it out.. Could it be the heater control valve?
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There is no "heater control valve" on an Expedition.

Instead, after you verify there is hot coolant going into and coming out of the heater core, look inside the vehicle. You may have a temperature blend door actuator failing. This operates the door between heat and air conditioning and could be inoperative.

Good luck.
i changed the thermastat and when i turn on the vents it blows hot an then turns cold.
I also have a 98 ford expedition, Eddie Bauer edition, with the same issue. I flushed out the coolant system, replaced the thermostat, replaced the water pump, and replaced the vent door and the vent door actuator. the vent door actuator can be accessed by removing the center council, it is located under he dash by the passengers left foot, its hard to get to but can be done in your garage. after all of that work, I ended up flushing out the heater core and replacing the coolant temperature sensor. again its affordable but a pain in the ass, if you do it your self. I paid $45.00 for the water pump, $22.00 for thermostat, $45.00 for the actuator. plus the coolant so all under $200.00 and a lot of swearing, don't forget to bleed the coolant system, that can be done by a few revs of the engine.. I used YouTube to guide me through the process... good luck and Semper Fi
I have a 99 Expo also replaced all that except the water pump. So after u changed all that is the heat working good on your truck
If you have the 4.6l engine there is not a heater control valve but if you have the 5.4l engine there is a heater control valve but location is very hard to find, I have searched everywhere!!!
The temperature blend door actuator is behind the dash.

A "heater control valve" is a valve that works in lieu of a electric blend door actuator on some cars. The Expedition does not have one. Neither the 4.6L or the 5.4L.
Check your fuses. I drove without heat for 4 years. Went to replace the blend door actuator and the old one worked after we tore apart the dash. I had a blown fuse. Go through your owners manual because there are several fuses that tie into the heating system. I had already had the radiator replaced, the heater core flushed and had several certified mechanics look at it. I have a 1999 Expedition
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