My heater doesn't work and I cannot figure out why. I have a 1994 f-150 351 windsor with a/c and no matter what vent option i put it on the heater doesn't come on even when it is all the way down on the red, and the tepature doesn't come out at all please help, I am kind of new to working on my truck but I know a lot

 

You'll have to explain a little bit further, is the blower motor running? As long as you have coolant in your radiator the coolant is flowing through the heater core and you have heat, the blend door just needs to open and the blower motor needs to turn on to get the heat out to where you are.

-Jon

 

Sounds like your thermostat is stuck open. This being you can feel air blowing and the operating temp stays pinned on cold.

 

the blower works you just can't feel the heat

 

so no air flow or just cold air.

 

Sounds like mark1111 is right. Change out the T-stat and see if that helps.

 

Blender switch ....... the thing you use to change from hot to cold For so reason if you use it like your supposed to it likes to break Mine just went out and I have work trucks that have had the same problem. Some "intelligent" engineer did a good job on such a simple switch.........saved about 5 cents a unit making a piece of junk like these. Not an expensive fix.....I think they are about $15.......the only problem is getting time to order one.

 

were can i get a blender switch, and how hard will it be to install one.

 

I put a new stock thermostat, and my heater still doesn't work ,and when I mention the blender switch to the dealer they have no idea what am talking about. I will clarify my situation. The heater doesn't work, air still blows out it is not warm at all, but it is not like cold as a/c, even when I put it on any of the choices such as vent defrost floor mix or even a/c it doesn't work it still blows but it simply is'nt worm and thats with the temp selector all of the way on max heat, I checked all of the connections and they were all good so I don't think anything is loose, and all of the wires were tight. My A/c still works though perfect. Also I don't have any evidence of the heater core because I cannot see any leaks or smell it so i am at a loss. please help

 

run truck and feel both heater hoses. are they hot. they should both be hot. if so thats good. you need to know if hot water is flowing through it. if one warm and one cold now you need a heater core or poss more. now to the temp selector sw. its the sw. in the middle of your control panel. the one that goes from blue to red. it operate a cable that sets the blend door to hot or cold. its a very simple operating sys. pull your glove box down. you should be able to see the blend door behind it. operate the temp selector sw. and see if that cable moves. or if the cable has poped off the blend door. it will be on top you might need a flashlight. if cable does not move, go to temp selector sw. pull the slim panel. the trim that goes across your dash form sterring wheel to the right door. pops off. two screws the panel, pops off. then four screws on the control panel. there are wires and cables connceted to it. so it will not come out far. now you can see that temp sw. move it back and forth. hope this helps it is a very simple sys. good luck.

 

I think these trucks also have a vacuum valve on the heater core supply hose. There is a good chance that a vacuum line hase gone bad. The blend door should also be operated vy a vacuum line...check the valve under the hood fisrt, just because it's easier to get to.

 

I checked the hoses and they were warm but not extremely hot, and they look farly new. Also all of the cables are connected and seemed to be operating perfectly. I would like to know more about the vacum hose though.

 

I think medic may be on the right track. I don't know how the 94's are set up, but my 74 has a vacuum operated water valve in the engine compartment that regulates the water flow to the heater coil under the dash. When it's open a bit, you get low heat, open it a lot, you get higher heat. On the 74's The valve is located close to the firewall in plain view. It has a vacuum operated dashpot on top with an exposed mechanical arm that makes it easy to view the operation of the valve. Mine was stuck closed when I bought the truck but it was cheap to replace. An old cracked vacuum line would also be a good place to look if that valve isn't operating.

 

I got it working finally it was the valves on the hoses that go into the heater core, they were closed tight, It works great now. Thanks for all of ya'lls help