1. Welcome to PlowSite. Notice a fresh look and new features? It’s now easier to share photos and videos, find popular topics fast, and enjoy expanded user profiles. If you have any questions, click HELP at the top or bottom of any page, or send an email to help@plowsite.com. We welcome your feedback.

    Dismiss Notice

Heater/AC/Fan problem and High Idle Installation

Discussion in 'Ford Trucks' started by scoot98758, Nov 12, 2008.

  1. scoot98758

    scoot98758 Junior Member
    Messages: 29

    I have a 2004 Ford F-350 and if I have my heater/AC/fan on and I switch into 4wd WHILE MOVING the fan sounds like it revs to its peak and the air stops coming out of any of the vents and when I change the speed of the fan it does nothing. However if I switch into 4wd WHILE NOT MOVING there is still air coming out of the vents until I start moving. Does anyone know how to fix this because I would really like to be able to plow in 4wd with the heater running?

    Also I am planning on installing a high idle switch and read on a few forums that all you need to do is hook up a few wires but in past years not all models had the wires. First does anyone know if the 2004 F-350’s had these wires or do I need to buy an AIC or something else? If so does anyone have a recommendation for a brand to get or a place to get them from? If the F-350’s had these wires does anyone know which wires to look for and where to look for them or a site that has instructions on how to hook it up?

    I really appreciate your time reading through this and for your answers/solutions
     
  2. scoot98758

    scoot98758 Junior Member
    Messages: 29

    Also, I forgot to mention that the AC/Heat/Fan works fine while in 2wd.
     
  3. festerw

    festerw Senior Member
    Messages: 986

    Is your 4wd actually engaging? I don't know alot about the Fords but it sounds like you've got a vacuum leak somewhere in the 4wd system.
     
  4. scoot98758

    scoot98758 Junior Member
    Messages: 29

    Ya I am sure it is engaging.
     
  5. stroker79

    stroker79 2000 Club Member
    Messages: 2,802

    its definately a vacuum leak! Check the connections at the hub to make sure they are not leaking. You may just want to toss in some Warn manual hubs, cap the vacuum line at the hubs and that should solve all your issues.
     
  6. ducatirider944

    ducatirider944 Senior Member
    from Iowa
    Messages: 469

    You have a vacuum leak, but it isn't in the hubs if your truck is locking into 4x4. Have fun trying to find it. Replacing your hubs with manual won't solve your problem, you still have to flip the switch on the dash to engage the 4x4. So even though you have manual locking hubs installed now, your truck will still send vacuum to the hubs and you will still have the leak that is making your vent system to not work.
     
  7. scoot98758

    scoot98758 Junior Member
    Messages: 29

    I'm new to working on trucks and would really appreciate it if someone could tell me a good place to start looking for the problem and if someone could post a picture of or describe what/where the vacuum lines look like.
     
  8. ducatirider944

    ducatirider944 Senior Member
    from Iowa
    Messages: 469

    Not to bash here, but if you don't know what vacuum lines look like, this is way out of your scope to fix. Vacuum leaks are about like electrical shorts, you can chase them for days and still be scratching your head.
     
  9. scoot98758

    scoot98758 Junior Member
    Messages: 29

    You are probably right but if I don't try to fix it then I will most likely never learn how to fix it and just take it to people to get my truck worked on which is something I do not want to do.
    On a side note this is my first truck and I am still in high school so I don't have any experience working on cars and trucks but I can rebuild lawn equipment and skid steers so sometimes I just need a little hint to get me going in the right direction. It would be great if someone could tell me a book or website that I could learn how to diagnose and fix vacuum lines.
     
  10. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Since your green to the 4WD system and how it operates on your truck scoot I'll try to keep this as simple as possible...

    The locking hubs on your truck are engaged by vacuum when you flip the 4WD switch...the vacuum is sent down miscellaneous vacuum lines and various hoses to the locking hubs. Theres a sliding lock ring inside each hub that the vacuum basically "draws" into the "locked" position...thus engaging the hubs. The hubs are sealed with various O-rings so the vacuum can pull the locking rings into place. The original source for the vacuum supply also supplies vacuum to your various heat/defrost (HVAC) functions. This is why a vacuum leak in this part of the system can (and will) affect both the locking hubs as well as the heat/defrost functions.

    Now, as many owners will tell you these trucks are well know for the seal to fail on the axle shaft that seals the inner side of the hub, creating a vacuum leak when the 4WD is engaged. But your case is slightly different since you mentioned that it only does it once the truck is actually moved. So in your case it;'s actually the internal seal inside the locking hub itself that has fail. The tip off is the fact that it doesn't leak (and affect the HVAC functions) until the locking ring actually moves into the "lock" position....and that in many cases won't happen until the truck is moved slightly in order to help the splines line up so the ring can fully engage...

    Bottom line, you don't need a crash course in vacuum diagrams....you need to check into replacing the hubs. And like the other guys already mentioned don't waste your time with attempting to fix or replace the factory hubs, pick up a new set of aftermarkets full manual hubs. Then simply plug the vacuum lines for the stock hubs. Much, much, more dependable. wesport
     
  11. scoot98758

    scoot98758 Junior Member
    Messages: 29

    B & B Thanks a lot your post helped me understand it completely. Does anyone have a recommendation of a hub to buy and the approximate price of the hubs? Also one more question, on my hubs there are 2 settings Auto and Manual. I assume that if its in Auto it automatically chooses to lock the hubs out and when in manual it is always locked out. How does switching from automatic to manual work with the vacuum system or is it a completely different system?
     
  12. stroker79

    stroker79 2000 Club Member
    Messages: 2,802

    I and most other switch to the hubs made by Warn. Mine were $170 at Napa and took about 5 mins each side to sway. just make sure you cap the vac lines there. the Warn hubs dont have an auto setting so you will have to get out to lock/unlock you hubs but I normally just leave them locked during the winter and turn the knob on/off in the truck.
     
  13. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    When they're in the "auto" position they can lock when called for...namely when you turn the 4WD dial to the 4WD position thus sending the vacuum signal down and locking the hubs with vacuum.

    When you turn them to the "manual" position your physically locking them by hand..ie the manual way. Just like on an older non auto hub equipped truck.

    So in a nut shel, the vacuum controlled auto position does the same thing as what your doing by turning them manually...you just don't have to get out in the cold to do it. :D
     
  14. massfirefighter

    massfirefighter Senior Member
    from mass.
    Messages: 128

    Last edited: Nov 15, 2008