Where is the heater control valve located on this truck? I have changed the thermostat, acid flushed the heater core, flushed the radiator, fluid is topped off, and still blows ice cold, so this is my next step. The controls work fine. I was told that the heater box needed to be replaced...exactly what this is I'm not sure. I'm thinking it's the housing for the blend control. Any ideas? Thanks in advance, Rich B.
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Re: 1998 ford f150- heat issue
There is no heater valve on a 1998 ford F-150. The hoses for the heater lead directly from the engine and go to the heater case. PS The heater doors are all vacuum controlled so you might wanna look under the dash for any lines that might be disconnected
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verify heat is in normal range using dash gauge. if its normal then good. if it is below normal, you may have a sticking open thermostat not allowing heat to build up enough for "hot" heat. but usually luke warm heat will be this issue.
If everything is fine with gauge heat, check the hoses going to your heater core with your hands. they BOTH should be hot. If one is hot and another is warm then you have heater core issues. If both are HOT then you may want to check your temp controls. either temp control may not be working or the door that changes temp may be stuck in the cold position... there are many things, but checking the heater core hoses are most likely going to reveal bad heater core.
You will need wiring diagrams and volt meter to diagnose anything other than touching hoses and looking at gauge.
the problem maybe heater core stopped-up. need to see if coolant is flowing thru heater core.and check to see if heater hoses are getting hot near heater core . if take off heater hoses to core with water hose run water thru one side of the hoses to see if water flows thru the other hose.
ok, i had the same issue, your thermostat is stuck open, or you need to check cooling system and the color of coolant, maybe try a flush, go to parts store and get some acid cleaner for flushing your cooling system.....good luck!
The only reason it won't blow hot air is because the water is not getting to the heater core. Check to see if you have a heater control valve in one of the two lines to the heater core. If so check to be sure that is is opening and closing. If it won't open then you get no water flow in to the heater core.
If it has a heater control valve you can easily locate it. You will find it on one of the two hoses going to the heater core. Check to be sure it is opening. Also check to be sure you heater core is not plugged.
The problem may be the switch that controls the temp of the air. It may be out, or the servo it controls may be out. To test this you have to take a lot apart as the servo is located inside the heater box. I would have a mechanic look at it. It could also be a bad heater core. Water leaking into the floor is a good sign of a bad heater core.
You may need to remove the hoses from the heater core inlet an outlet and flush it directly, I saw these get plugged up on many cars like yours while I was a Ford technician, direct flush of the core cured the issue.