log

I have a 1997 f150 that has no heat the fan works but only blows cold air.Already flushed heater core and had lots of flow through it.But did notice that with the truck warmed up one heater hose is warm the other is cold.Thinking there is a mixing valve somewhere on those line but can't see where does anybody have an idea what might be the problem and if there is a mixing valve of some sort where might it be located?

dewman

You can check to make sure you have enough coolant in the radiator. Low coolant levels can cause lack of heat too. The mix of heat/cool is from the blender door. That allows more/less cool air in to mix with the warm air off the heater core. If you have 1 warm hose and 1 cool hose, maybe there is blockage in the 2nd hose not allowing the coolant to circulate. Both hoses should be warm/hot to the touch.

Good old Bill

X2 to dewman. Both heater hoses have to be of same temp (appx.) to show flow thru heater core. Don't know when Ford discontinued the heater valve located in engine compartment. Just trace both hoses from engine to firewall. No valve is no valve, engineers stuff why its not used anymore. Hoses of unequal temp is no flow, obstruction or air in system. If hoses are of equal temp and near same temp as upper rad hose, then the system is good. No heat is blend door inside heater plenum inside cab.