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No air coming out of floor vents on my F350.

Discussion in 'Ford Trucks' started by mklawnman, Jan 3, 2012.

  1. I have a 99 F350, and when I turn on the vents for the floor vents the air doesn't come out by the floor, it only blows out by the defrost vents. IS there some baffle inside the vent unit thats not opening or closing? Or could it be the switch in the dash to change what vents to have on?
    Any help would be appreciated.
  2. I'm not 100% sure on this but judging by your sig im assuming the truck is a diesel, i had the same problem on my 04, don't know if 6.0 or 7.3 is different but there is a hose that comes off on the vacuum pump that makes the vents switch and it comes off on a lot of trucks. Open the hood and look at the passenger side towards the back and see if there is a vacuum hose flopping around in there.
  3. Its a 7.3L Diesel. Ill have to check those vacuum lines hope its obvious cause I know there are vacuum lines for the 4x4 as well so.
  4. Yeah check that first, if its blowing out but not changing where it's coming from that's gotta be it.
  5. tugboat609

    tugboat609 Member
    Messages: 55

    Had similar problem with a Dodge I used to have. Was vacuum line.
  6. dieselss

    dieselss PlowSite Fanatic
    Messages: 11,395

    Also check behind the glove box. That's where the blend doors are. You can see them easily working or not.
  7. hunt 444e

    hunt 444e Member
    Messages: 62

    start your truck turn heat on go under hood passenger side by the firewall is your mode door actuator little black box about 2x 4 or so if thats clicking or making noise take it off throw it out get another you probably washed it and got water in it or something :mechanic::
  8. fordsuvparts

    fordsuvparts Senior Member
    Messages: 135

    IF you will look under the passenger side of the dash there is a vacuum plug that can come unplugged and it will cause the floor vents not to work. This happened last winter on 2 different trucks someone jammed there feet under and pulled it loose.
  9. Well I checked the vacuum lines on the passenger side under the hood but everything looked fine. I did see where the lines go into, some box, but I dont think anything is clicking or if any vents are. All settings for the vents seem to default to the defrost, A/C, everything.
    I will check under the dash on the passenger side and see if I can find a vacuum plug line. Also might look into that box under the hood where the vacuum lines go into maybe thats bad?
    I think this problem has happend since I bought it back in Oct of 2010, and before that the truck didnt get used alot so maybe something just froze up without getting used alot.
  10. alldayrj

    alldayrj PlowSite.com Addict
    Messages: 1,108

    the lines leak, so the pump runs 24/7 and burns out. you're probably going to need a new pump. my buddy found the leak with a vacuum tester and we put the new pump in and everything works great now.
  11. Where is the pump located? ON the firewall on the passenger side? How much is something like this to replace?
  12. TwiceStroked

    TwiceStroked Member
    Messages: 40

    Passengers side inner fender, black about the size of a small shoe box.
  13. tjctransport

    tjctransport PlowSite.com Addict
    Messages: 1,390

    default setting on the ford heater controls is defrost. if nothing works but defrost, you have a vacuum leak.
  14. Should I get a vacuum tester and see if it is just a leak in the line? or could it be that the pump is bad? Just wish I could find a diagram of the vacuum lines or something of that nature ha. Are these vacuum lines the same ones that go to the 4x4 system? I know I dont have the locking hubs working anymore, I have to manually turn them to get in 4x4 which isnt a problem, Id rather do that since I know it is in 4x4 mode.
    Last edited: Jan 4, 2012
  15. dieselss

    dieselss PlowSite Fanatic
    Messages: 11,395

    no you dont need one. its a black box on the pass fender well. just a little bit behind the pass battery. if you turn the truck to "run" you might be able to hear it. maybe not..if you unplug the vac. lines going to it. the pump should run if its working.if not then you need to check for pwr and gnd at the connector. if it runs then you have a problem else where in the system that you need to find.
  16. tjctransport

    tjctransport PlowSite.com Addict
    Messages: 1,390

    if you have electric shift 4X4 with auto hubs. check the front axle for leaks. that is usually where the vacuum leaks are.

    and yes, a vacuum gauge is the only way you are going to find the leak. start at the pump and work your way out. when sooner or later you will loose the vacuum at a line and then you will know it is that line that is bad.

    don't be surprised if you find more than one bad line.
  17. plowguy43

    plowguy43 PlowSite Fanatic
    Messages: 5,281

    My buddy replaced the vacum pump on his 05 Diesel by himself, got it online for $65 I believe. He is not mechanically inclined and was able to do it easily.
  18. Drottlawn

    Drottlawn Senior Member
    Messages: 364

    I would put my money on the front hubs leaking and causing your issues. My old truck used to do the same thing until I got the front hub seals replaced. Then everything worked as it should including my auto hubs. Didn't realize what I was missing! Very Very common problem on these trucks.
  19. mrv8outboard

    mrv8outboard Senior Member
    Messages: 205

    Here are a few things to try and help. It does sound like your vacuum pump is bad.
    Last edited: Jan 5, 2012
  20. Well I think its a bad vacuum pump. I checked on my F250 7.3L Diesel and ran the climate controls and the vacuum pump ran for a bit then shut off, and in that truck I am getting air out of the vents and to the floor so that truck is working fine. On my F350 the vacuum pump didnt run at all when I turned the climate controls on.. So I think that is what is wrong. If i get a new pump and my Auto Hubs are still bad my guess is that the pump will wear out since I do have a leak at my hubs. So until I get the hub vacuum lines fixed or get new hubs Ill have to deal with the heater going to defrost default for now.
    Last edited: Jan 5, 2012