The other day I had nothing but heat and plenty of it. Turned the heat off and then had no heat at all. It stayed like that for a couple of days until last night. I started the truck and the heat was stuck on again.

I'm not sure where to start looking for the problem. I thought it might be a stuck thermostat, but my engine temp gauge is normal. Also, the temp **** on the a/c seems to be intact.

I'm armed with my trusty Haynes manual if ya'll can point me in the right direction and what to look for.

 

Sounds like a blend door that is binding/sticking or is broken.

Steve

 

so what would be the solution to fix this problem? afraid to ask but is it a problem that the whole dash has to come out to get to the blend door?
Im asking because i have experianced the same problem before and never figured out what to do with it.

thanks

 

See the other posts. There is a service bulletin out to dealers for the necessary repairs.

 

I have a '99 F150 w/ 5.4 and my similar problem seems to be vacuum related. To get heat I drive a few miles to build engine heat, switch to a/c and cold, stop and accelerate from the stop fairly hard. When you feel the heat coming through the vent switch everything to floor and warm then I'm good to go for that trip. This takes less than 50ft. If after 50ft or so and it didn't work, do it again accelerating a little harder. Back in the summer a/c was all fine on the highway but if I came to a stop you could feel the heat kick on. Not a daily driver so this works for me for now.

 

That is NOT a vacuum problem since the temperature blend door is not vacuum operated. Only the inlet and outlet dampers are controlled with vacuum.

You have a sticking/binding/broken blend door flopping around in there. Eventually, your work-around will no longer work, so keep your fingers crossed that it lasts as longs as possible.

Steve