Heater Control
 

My 1993 F 350 is without heat, AC works fine, just picked the truck up in Florida, back in Michigan it is cold. The heater hoses are hot up to the fire wall so I think water is flowing through the heater core. Is there a heater control module that might not be working? Where is it located and what does it look like.
Thanks, Froze in my Cab

Not sure on the 93 but on the 86 there is no water control. Heat is regulated by a vacuum operated door that controls where the air comes from on one side, and where it goes to on the other side.

The door controller is behind the glove box on mine, it may have had something drop in the defroster vents and block it in the cool position.

Hey Dave, I've got an '86 and my cab seems to stay warm all the time. A little too warm. Nothing I do on the control panel helps.

Can you describe what to look for behind the glove box?

Thanks in advance.

Erik

Dave, one other thing. I can't seem to get air to come out of the air vents. Only on the windshield and I believe the feet area. I know for sure the windshield defroster... not 100% sure on the feet area.

Howdy Erik . Check your vaccum going into the cab . Could be a bad ac/heater control switch also. If you remove your heater core , you will see the door dave is speeking of . I know this because mine is broke . I have to replace the door to make my vents operate properly .I don't remember if the door is vaccum or cable operated .I'll look at mine in the morning .

Jayrak . Your heater core could be clogged . I had to flush mine today . Took me a little while , but I finally moved some water through it . Both my heater hoses were hot even though there was no water moving . Anyhow , something for you to look at .
Good luck .

Sounds like you vacuum is low.
The selector valve is vacuum operated, if you loose vacuum it defaults to the defrost position.
Also you should notice lots of foot pressure required to stop the truck if it is the pump.

my 89 would not change vent positions because of a vacuum leak in the line going to the selector valve thingy below the dash. I dont think that controls the heat or cold, just where it blows out.

HOld on now, if 93 is the new body style then the heater controls are just knobs that are electronic I thought. They are completely different then our 83s-91s.