Okay.... 1999 F-150, a/c, manual transmission.........Like many others, I have no heat, but I also have a twist to the problem. It also seems that my selector switch won't switch from defrost no matter what selection I put it on. Any ideas?

 

Blend door actuator and maybe heater control valve theres my ideas lol

 

you have two different problems--- maybe. First check that temp gauge is "normal" and heater hoses are hot, and radiator is full. The heater controls work like this... THe air direction of flow is controlled by vacuum doors inside the ducts. If the vacuum is lost, the default is to blow air to the defroster. You can have a bad vacuum hose under the hood, at the fire wall, under the dash, or the controller on the dash could have a crack back by the hose connection... Second, the water flows thru the heater core all the time. The heater is always hot. Your control heat **** moves an electric operated door called "blend door" to mix cool air and the hot air from the heater to get the selected temp. The door can be broken, the cam on the motor to the door can be broken, or the motor can be bad, or the selector **** on the dash can be cracked and slipping on the shaft.

 

New info for y'all. The selector switch is working fine, it is ONLY the temp adjustment that isn't working. I checked the 2 hoses going thru the firewall and assuming that I checked the correct thing, they are both cool to the touch after 20+ minutes driving. This isn't right. I am at a loss. To add to the intrigue, the coolant level in the reservoir isn't changing at all whether the engine is hot or cold. It ALWAYS is at the same level. My engine temp after 20 min. driving is perfectly in the middle of the gauge.

Any ideas now?

Thanks in advance.

Robert

 

Im thinking plugged up heater core....IF you feel sure you have the correct two hoses,dis-connect them from the engine,and put a water hose to one of them.If water comes out the other one with around the same force as the input,Im at a loss...If it doesent,you have either a plugged heater core,or one hell of a restriction somehwere.

 

Well, I realized that I was checking the wrong hoses. I got the correct ones and after 30 minutes driving, they were close to the same temperature. They are "Warm" to the touch. No where near to hot to hold onto as I have read others say about their lines. Should they be REALLY hot or just warm after 30 minutes driving time.? I'm wondering if this points to a thermostat that is stuck open. Is there a way to test this? The only problem with this theory is that the engine temp guage in the dash sits right in the middle after 5-10 minutes driving time.

Also still confused by the fact that the radiator overflow level never changes whether the engine is hot or cold.

 

PROBLEM SOLVED!!!!!!!!!!!!!!

It was a broken control ****, of all things.

I tried at an earlier time to get the **** off but couldn't get it to budge. I revisited this because I noticed that at one point in the turning of the control **** from hot to cold it would get to a point where it would seem to settle into a position on its own. I took the heat/AC control panel off and was able to get the leverage I needed to pull the **** off. Sure enough, it was cracked on both sides of where the post sticks in. I'm not sure how much Ford will charge me for a new ****, but I bet it will be less than the $800 labor to replace the heater core. =)

Thanks so much to all who chimed in with their wisdom. Even thou the problem might not have been exactly what was offered, I still learned a lot about the heating system of the truck through your knowledge and willingness to share that knowledge.

 

I believe Steve suggested to check for a cracked **** slipping on the shaft.

 

Yes he did. And like I said, I tried it earlier and couldn't get the **** off. Today was the first time I was able to ge it off. I went to the dealership tonight and after $10 I am back to normal.

 

well, your $790. in the BLACK... thats great!