Question Heater control

Discussion in 'PowerStroke Diesel Excursions' started by Chewman, Dec 21, 2013.

  1. Chewman

    Chewman SDD Junior Member

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    I come to the guru's of Ford again!

    My 2001 X 7.3 is only blowing heat in defrost mode.

    Vac pump sucks but the heat module that moves when you change from defrost to heat doesnt. It will snap into defrost mode fast. If I manually pull up on the rod it will sit in heat but once I turn the knob it wont go back. When I unplug the vac line from the module I can feel it suck. Not hard, but you can feel it.

    Where are the weak links in the vacuum system?

    What's the easy way to test everything to rule things out?

    Thanks

    Chewman
     
  2. Chewman

    Chewman SDD Junior Member

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    Also: What should the vacuum pump measure when I put a guage on it?

    Thanks

    Matt
     
  3. DaveBen

    DaveBen SDD Senior Member

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    You have a problem with the vacuum hoses near the front axle. The Auto 4X4 has a leak going from the frame to the hubs. OR the hubs are leaking. What you are seeing is the default for the heater system.

    Dave :dunno
     
  4. Chewman

    Chewman SDD Junior Member

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    I have next to the vac pump what looks like an electric switch that sends vac down to the frame. I plugged off these lines and still had the problem. I thought that this would be the vac control for the lock outs. Am I wrong?

    Thanks

    Chewman
     
  5. DaveBen

    DaveBen SDD Senior Member

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    I would think so, but I have manual hubs and transfer case. I would never have auto 4X4. :dunno

    Dave
     
  6. BIG JOE

    BIG JOE Full Access Member

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    Process of elimination. ( things are 10 years old now)

    Replace both hub vac lines.

    Check the line from the vac pump.. to the accumulation tank.. and the tank itself, for leaks.

    Remove the glovebox.. up and to the left will be the heater control vac manifold. check all the vac and mechanical lines, to and from the manifold.

    Joe

    If ANY of the lines look dry or cracked.. replace them. (Patching works for awhile.. but yul be back at it ?)
     
    Last edited: Dec 21, 2013
  7. Chewman

    Chewman SDD Junior Member

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    Thanks Joe!
     
  8. Dogman

    Dogman Full Access Member

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    One thing to get is a hand held vacuum pump. It's great for checking areas. One of the first places to look is from the vac. block near the pump to the vac. line that goes in to the cab. It's on the right side/passenger side, next to the blower box. Hook to this line and use the hand held pump and see if it pulls down and hold the vacuum. If it does move the switches and pump it down again and see if it hold. If it all holds your good. If not it's a good chance the vac. control switch is bad. Your A/C controller but look over the lines too.
     
  9. RSG

    RSG Full Access Member

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    Also...the recent leak on my '02 turned out to be the vacuum seal at the passenger side front. Yes, by unplugging hoses but plugging the barbs at the vacuum box by the pump, you should eliminate hoses AND seals and be able to eliminate one by one. My hub lines are still original. But hub seals? Replaced one twice, and one once, since 2004.
     

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