swampedout Posted June 11, 2023 Share Posted June 11, 2023 Hi everyone! Its been quite some time but Im still tinkering with the truck when I find time. Ive switched jobs recently and considerably shortened my commute so Im planning on using the bull as a daily driver in the next couple weeks. However, since its going to hit 90F this week, Im sorting out my issue with the hvac controls. Right now its stuck in heat. There is a broken white plastic that the temperature selector clips onto behind the control panel. Is the temperature selector related to the heat/ac switch? Do I have a missing vacuum hose from the control module? I looked thru the documentation (which does a great job at explaining the refrigeration side of the ac system) but I guess I need a dummy guide as far as what Im missing behind the control panel to select AC. Thanks, Sam Link to comment Share on other sites More sharing options...
Gary Lewis Posted June 12, 2023 Share Posted June 12, 2023 Sam - What page of the documentation were you looking at? On the one at Documentation/HVAC/HVAC Systems you can find factory shop manual sections that go into detail on how the systems work. Have you looked there? Link to comment Share on other sites More sharing options...
swampedout Posted June 12, 2023 Author Share Posted June 12, 2023 Sam - What page of the documentation were you looking at? On the one at Documentation/HVAC/HVAC Systems you can find factory shop manual sections that go into detail on how the systems work. Have you looked there? Hi Gary, yes I was looking at that page. Maybe its because I was on my phone, I will read through it on the desktop tonight. My question is about the parts labelled 19988 in this diagram. I can only locate 1 behind the controller in my truck but the tab that has broken has clips to seat two. Link to comment Share on other sites More sharing options...
Gary Lewis Posted June 12, 2023 Share Posted June 12, 2023 Hi Gary, yes I was looking at that page. Maybe its because I was on my phone, I will read through it on the desktop tonight. My question is about the parts labelled 19988 in this diagram. I can only locate 1 behind the controller in my truck but the tab that has broken has clips to seat two. Yes, there are positions for two cables, but I believe there is only one cable used - the temp control cable. Ralph, is that correct? Link to comment Share on other sites More sharing options...
swampedout Posted June 12, 2023 Author Share Posted June 12, 2023 Yes, there are positions for two cables, but I believe there is only one cable used - the temp control cable. Ralph, is that correct? Maybe that isnt my problem then. I can change the temperature but its stuck on heat, even when I select AC. Link to comment Share on other sites More sharing options...
81-F150-Explorer Posted June 12, 2023 Share Posted June 12, 2023 Yes, there are positions for two cables, but I believe there is only one cable used - the temp control cable. Ralph, is that correct? It depends on the year, but on A/C models using one cable, this is correct, as the A/C side uses vacuum control actuators. Link to comment Share on other sites More sharing options...
81-F150-Explorer Posted June 12, 2023 Share Posted June 12, 2023 Maybe that isnt my problem then. I can change the temperature but its stuck on heat, even when I select AC. Sounds like the temperature blend door is broken. The infamous hinge breakage that happens to the door. There is a member here who makes them if I remember correctly? That would be the first thing I'd check. The temperature cable could also be slipping, removed or broken from inside the engine bay where it hooks to the heater-A/C box. The vacuum controls are also a cause of failure in these trucks. However they can be fixed using O rings, and such, but I have never done the job, so do not know how easy that fix is. Link to comment Share on other sites More sharing options...
swampedout Posted June 12, 2023 Author Share Posted June 12, 2023 Sounds like the temperature blend door is broken. The infamous hinge breakage that happens to the door. There is a member here who makes them if I remember correctly? That would be the first thing I'd check. The temperature cable could also be slipping, removed or broken from inside the engine bay where it hooks to the heater-A/C box. The vacuum controls are also a cause of failure in these trucks. However they can be fixed using O rings, and such, but I have never done the job, so do not know how easy that fix is. Thank you both for the guidance so far. I have another question about the dash selector. When you are switching between heat and AC does it prevent you from going between hot and cold? Meaning can you put the slider to cold air while on a heat setting and visa versa? Im trying to retrace my steps to before it broke. Link to comment Share on other sites More sharing options...
ratdude747 Posted June 12, 2023 Share Posted June 12, 2023 Sounds like the temperature blend door is broken. The infamous hinge breakage that happens to the door. There is a member here who makes them if I remember correctly? That would be the first thing I'd check. The temperature cable could also be slipping, removed or broken from inside the engine bay where it hooks to the heater-A/C box. The vacuum controls are also a cause of failure in these trucks. However they can be fixed using O rings, and such, but I have never done the job, so do not know how easy that fix is. That's the Heat/Defrost door. Best fix is the 3D printed doors: https://forum.garysgaragemahal.com/Heater-Blend-Door-Alternate-Design-tp112193.html But, those didn't exist when mine failed, so I used a modified piano hinge: https://forum.garysgaragemahal.com/Lost-all-vent-controls-tp93943.html (lots of links in there). Link to comment Share on other sites More sharing options...
swampedout Posted June 12, 2023 Author Share Posted June 12, 2023 That's the Heat/Defrost door. Best fix is the 3D printed doors: https://forum.garysgaragemahal.com/Heater-Blend-Door-Alternate-Design-tp112193.html But, those didn't exist when mine failed, so I used a modified piano hinge: https://forum.garysgaragemahal.com/Lost-all-vent-controls-tp93943.html (lots of links in there). So just to clarify: I am getting heat at all times, even when I switch to AC. So far what Ive read about the blend door is that it directs the airflow to the vents, floor or defrost. Like I said before, I really dont understand all the basics of this system so I just want to make sure before I pull the dash and replace the blend door to fix this issue. Link to comment Share on other sites More sharing options...
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