1998 Ford F150 Heater Hose Diagram

1. 

   oldie63

   hello FTZ, im new here and am looking for some help with my 1994 f150 xl.
   ive looked on various sites n forums for he same problem im having but everyone has a similar and or related provlem but not the exact same.
   My heater has a problem wit providing airflow to the floor, every other setting seems to work ok ut maybe i'm missing how much is or isn't working as it should with the mix setting.
   From what I've aleready read is that the default setting is to defrost. I have that on heat in floor position, and mix, defrost works as it should seemingly. On vent i get heat and ac and defost but no floor or mix.
   I'm stumped as to where to begin?

2. 

   dustybumpers Article Contributor Founding Member

   You have a broken vacuum line, under the hood, on the passenger side, by the heater box
   The line is plastic, and heat bakes it into a powder, There are actually 2 lines there, a black one ( vacuum supply)
   And a white one ( vacuum to actuator)
   The black one goes into the cab, the white one comes back out, and hooks to the actuator right there by the heater hoses.
   That actuator opens and closes the blend door
   The blend door goes to defrost as default, when there is no Vacuum
   I don't have an actual picture, but if you look in this one where I replaced the dryer,
   #ad

   to the left is the actuator, the line coming out is the one I repaired on this truck, should be white on yours
   Follow it into the wiring harness, and replace it back to where the heat has not harmed the line
   In the same area in the harness, the black plastic line will need to be repaired too, it goes from the harness to the side of the heat box
   This is another repair, that has the plenum off, but shows where the black line finally ends.
   Don't forget to test the check valve
   #ad

   56panelford and RexB like this.
3. 

   FTZ HAIC Staff Member Founding Member Vet Zone Leader

   Same thing happened on my 2004 F250, in my case the vacuum junction box under the hood was cracked.

4. 

   dustybumpers Article Contributor Founding Member

   80-91 could be a rusted out vacuum can reserve, on the passenger inner fender, but in 92, that tank became plactic
   If he were having trouble with his cruise control, I would say reserve can rust through, that is located below the coolant and washer tank behind the driver's head light inside the core support. That one is still a "juice can"

5. 

   oldie63

6. 

   oldie63

   Dustybumpers, is that blend door actuator the one right in the corner neat the hood hinge and the corner of the fender and windshield?

7. 

   dustybumpers Article Contributor Founding Member

8. 

   oldie63

   Thanks I just went out and basically propped it in the opposite direction the vacuum or internal spring has it in one position, started truck and turned on fan and floor position control, no change, 98% of airflow still going to windshield, so it can't be that actuator or something is broken inside heater box?
   Is that possible and a more or less easy fix like removing outer heater box housing?
   What next?

9. 

   oldie63

   I have two lines going to Juice can one red and one black, I have I think red and green lines coming from harness down by engine. Gettin dark to see now without light.

10. 

    dustybumpers Article Contributor Founding Member

    Green is EGR, Red is ported
    the 2 lines you need going there are black ( main vacuum) and white ( control line from heater knob) Those 2 are in the wire harness by the heater box.
    I will see if I can post a picture for you as soon as it's day light here.

11. 

    dustybumpers Article Contributor Founding Member

    Busy day today, sorry for the delay
    here is the actuator on my 94
    #ad

    and the repair into the harness
    #ad

    #ad

    Juice can
    #ad

    Then opened the hood on the 89 next to it, just because I knew it was never done, and was acting up
    lines coming out of wiring harness
    #ad

    #ad

    #ad
    o
    oooo, found the problem
    #ad

    #ad

    As you can see, when "someone" ( Tom) slammed the hood on the truck when I was changing the fender, and the hood hit the positive post on the battery, the ground strap heated the vacuum line in two, causing the actuator to no longer work!
    Pretty sure this is when he pushed me off the same truck and broke my shoulder too........

    Funny how we find things

    .

    IDMooseMan and RexB like this.
12. 

    oldie63

    
    HI no problem with Cruise Control just the floor, and mix part of the heater control.

13. 

    oldie63

    
    Hi I'll check as much as I can and then post some pictures if I can.

14. 

    oldie63

    Hi Dustybumpers my juice can is in fact metal not plastic, and since then my cruise control has failed and drivers air bag light has begun blinking but horn still works so not what I'm figuring for that dilemma a broken clock spring?

15. 

    dustybumpers Article Contributor Founding Member

    Probably so. Not too hard of a fix. I'll have to look and see if I took pictures when I did the 94.
    I think the whole project took about an hour start to finish

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Source: https://www.fordtruckzone.com/threads/1994-f150-heater-problem.661730/

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