I just bought a 1989 F-150 reg cab 4x4 and just found out that the heater is not working, it blows air and and gets about as warm as if it was just on vent. The air has no smell to it and I could'nt find any leaks if anyone has any tips or information about this I would be very thankful. P.S. also my temp gauge is not working and the motor seems to be running at normal temp.

 

Two things come to mind:

1) The previous owner may have bypassed the heater, possibly because the heater core has a leak.

2) Air is not passing over the heater core because parts of the system are missing or not opearting properly.

 

if that doesn't work,flush your cooling system until the water comes out crystal clear(if there is any indication of scale build up,dirty brown crap in your coolant)and refill with new coolant.
but first make sure your blend door is opperating properly

 

Thanks for the info i'll give those thing a check and let you know what happens.

 

the temp control valve might not be working. maybe broken or cable came off. when the engine is warm feel the heater hoses where they go through the firewall. if they are both hot them the contol valve is ok and you have coolant flow through the core and sounds like a blend door problem, if 1 is hot and 1 is cold or warm then you have a flow problem, control valve, pinched hose or clogged core.

 

this might sound like a dumb ? but Im going to ask it anyway what is the blend door and where is it. Also how can it be checked. The hoses going into the firewall were hot so this sounds like it might be the prblem. Thanks for the great tips guys they are really helping me out.

 

I was informed a while back on this board that these newer (97-up) F150's no longer used a temp. control valve in the heater core lines.
That the core ran at engine temp all the time and that the blend door did all the temp. regulation.

Is this not true?

Gene

 

triumphman


97 and up use hot and cold air with the blend door to regulate the temp. But My89f-150 has an 89 so he uses a control valve.
correct me if i'm wrong but i dont work on this stuff much.

 

I'm guessing that there's enough antifreeze in the system ........... right?

 

yeah it is full got anything else for me?

 

Check the Tstat.

 

lees99f150,

Thanks, I just wasn't sure what year they started using (or I should say stop using the temp control valve).

My89f-150, I would bet you have a vaccum control problem or damper door not working in the duct system.

Can you get up under the dash and see any of the vaccum control modules that open these doors, to see if they move or feel if they do? Does the air flow shift between the floor. dash, and defrost outlets?

Because you have "hot hoses" going into and out of the heater core, I would think that the water side of the system is working fine.
But then, you allready said that. I'm betting on the duct system!
A vaccum control or vaccum line problem.

Gene