JimLF-150

Hi there I am new here so be easy on me Anyway I have a 1999 Ford F-150 Lariat with the 5.4 triton.

(1) When I drive my truck it blows cold air no matter what position I put it in on the dial.

(2) I have reved the motor up to see if maybe it would blow some warm air..no deal it would not.

(3) I have bought a new thermostate that when it goes bad it goes bad in the open position.

(4) I have not changed it yet because when I first fie the truck up to go some place the guage starts out normal and moves its way up as it warms up and stops just a little past the middle.

(5) some say its the blender door that is broke.How do I know for sure it is the blender door.

(6) Is there a way to check the motor and the door while it is still in the truck or do I have to pull everything out to check Both.

thanks for your help....God bless

akdoggie

Which AC system do you have? Turnable dials or the electronic controller? If it is the turnable style, blend door most likely. Electronic can be the controller head, or blend door.

Check by turning the dial and listening for the vac to switch. If you don't hear it or do and it doesn't change, blend door most likely broken at the mount point. If electronic, try the different outlets. If no sound, check the vac pods for vac. You can open the glove box and see into the area. You'll have to pop the box out of the top holder, but it bends easily to allow access. You may have to check your service manual for the exact way to check the electronic controller. It's fairly straight forward, but can consume a lot of time if you have to cut and modify your dash. Longer if you remove the entire dash assembly. There are several writes up on here about the blend door replacement. Type in
"blend door" in the search forum. You'll find enough reading to keep you busy for a while. Good luck

JimLF-150

Hey I changed the water thermostate today. Was easy as 1-2-3..No leaks..anyway went for a ride with the grandson in the back and drove it till the temp needle was in the middle.Turnned the dial to all on the dash everything changed and was still blowing cold air. drove it around then went back to the house waitted about a hr went for another ride went through all the diffrent defrosters floor and def still cold air i was driving and I heard this pop or something and then the air got warmer.Not as hot as it use to be but it did get warm.I left everthing the same when I parked it I am going to take it for another drive as soon as I am done posting to see if it does get warm again..I am not sure what kinda AC I have it is original..not sure what to think..I will leave a photo of the dash.... I have turnned the dial and I can hear the vacum closing and opening that is not the blending door right...the blending door just open for more heat and closes for less right.....Thanks

03Fordzilla

What you have is the manual type, and akdoggie was right. I'd say your blend door actuator has gone bad and needs replaced. I just replaced one in a 2002 explorer and they didnt leave much room. I think these trucks have more room for this, but not sure. They should be about $50 at an autoparts store. If you dont replace it with the motorcraft and go aftermarket i reccomend Borg Warner (BWD). If I cant get something that is motorcraft, I use BWD because I have never had one fail me yet. Hope this helps ya.

akdoggie

The vacuum pods usually always work. The door itself, breaks at the mounting end, causing the door to stick where it breaks or to swing freely. They are made of too much plastic for a high movement part to endure over the lifetime of one of these trucks.

JimLF-150

Thanks..Is it the door always that breaks never the motor that opens and closes it.

akdoggie

Yeah, about 99% of the time it is the plastic mount that breaks. The pods usually never go bad in the mechanical AC systems. They have problems with some of the electronic systems. Why, who knows. Same type pod, but some do lose the vac holding ability, but not usually on the manual AC.

capef150

I had the same issue (99 5.4) and flushed the radiator today. I left the flush in with just water to drive for a couple of days, and when I got in the heat was blasting! I will let you know if it lasts....