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Ford F-Series Climate Control

I need a direction to go before i dig into this. I have a 99 F-150, standard cab with the V-6. I have a problem with the climate controls. The Fan Blower works in all speeds. The A/C works, and the Heat works. But no matter where i turn the far right knob(to tell it where to blow i.e floor, dashboard, vent etc...) it always comes out the defroster vents. It will blow A/C and heat, but it will only come out of the defroster regardless of setting. Any ideas.


  • You have a vaccuum leak. The air diverter in the dashboard that directs the air around for the different settings is vaccuum actuated. The default position (and for safety's sake ) is Defrost. Either the vaccuum line that goes into your climate control system has fallen off or is leaking. Or you have a bigger vaccuum leak somewhere else on the engine that's not allowing enough vaccuum pressure to get to the control and is affecting your vents.

    Start checking all the lines - look for obvious disconnected lines, then check each one for holes or cracks. The vaccuum lines should be smooth and pliable. If a line line is stiff, brittle, or cracked replace it.

    Not sure about your model F-150, Ford may not use the typical black rubber vaccuum lines to go to the climate control on your truck. It may look almost like its colored wire about a quarter inch in diameter going up to the climate control air box up on the firewall.
  • Just purchased a new F150 super cab 4x4, this is the 4th I have owned.
    I very dissatisfied with the heating system, no matter what control you set it at very little to no heat will come out on the floor. Dealer removed dash replaced components and still the problem exists. They indicated all trucks on their lot acted the same way. Guess I am stuck with cold feet.
  • I totally agree with you. It takes a long time before the feet get the heat! I have the same problem with my 04' 150.
  • i have a ford 2001 f 150 truck. Just recently my ac and heater started to have a problem. When my truck is running i will have my ac dialed in to cold but every 20 to 30 seconds i can feel the heat come through then it will go away. I disconnected the climate control knob so it will hopefully not fluxtuate.Its kinda workin i have ac on the two closest vents but the other two closest to passenger has a slightly warm air coming through.Also when i did have the climate control connected I would have the truck running in idle i can hear what i think is the blender door moving even when the climate control is stationary. Need some opionions on what might be wrong. Thanks
  • fordtuf1fordtuf1 Posts: 5
    I don't know if this applies but ... on my F250 the vacuum for the heater/ac vents is shared. Of all things it is shared with the auto locking 4x4 hubs.

    I found this out when I was looking for information about serviceing both differentials and the transfer case.
  • Have the same problem as message above. Every few days I burn a breaker that controls the floor/vent/defrost selector control. It seems to be related to my backup lights also. Think it is fuse #28 under dash on 2001 f-350.
  • 0patience0patience Posts: 1,542
    Fuse # 28 is for the Brake shift interlock, DRL Relay, Speed control Module, Vacuum pump motor, hublock solenoid, back up lights or digital transmission range sensor, heated seats, parking aid module and trailer electronic brake feed.

    So, what pops the fuse?
    What doesn't work?

    The blower motor relay is on fuse 22 circuit.
    The realy controls both the motor and the floor/panel/defrost mode.

    One thing to try is to disconnect the heater blower motor resistor. The plug in is close to the blower motor.
    It will run the heater motor only on high, but if the relay lasts, then the resistor is grounding.
  • Thanks for responding. The fuse is #28 that blows. the floor/vent/defrost selector switch and the backup lights seem to be the only thing it affects. There is no rhyme or reason to when. It will be okay for a few days and then blow. So if I try the experiment above do you think this will help isolate? Is the relay and that #22 circuit connected to the backup lights also?
  • 0patience0patience Posts: 1,542
    That is the strange thing. Fuse #22 doesn't affect the back up lights. Fuse #28 does, but doesn't go to the fan circuit.

    I think you may have more than just a fuse problem.

    Unplugging the resistor will help to determine if it is a resistor problem, which is often a cause of the relay going.
    So it is an easy test to eliminate it as the problem.
  • Thanks again. So if this resistor/relay is bad would it trip the #28 fuse? #22 is not blowing. You stated that #22 doesn't go to the fan circuit. I'm not sure if I made it clear that the fan speed selector is okay, but its only the floor/vent/defrost knob that defaults to defrost.
  • I posted an earlier message involvig my backup lights and heat switch blowing the fuse. I have worked on my truck and discovered that these were only coincidences. #28 is still blowing ocassionally though. Can't figure out why. How could I track a ground in a wire? Where would I start?
  • 2005 F250 SD, V10 Triton. Best truck I have ever had. I have only one issue that I have taken in to the shop for and it has re-occured. When the ac is on and I put it to "max AC" it will revert to the defrost vents. And it does not blow as hard. Is it more likely to be a vaccum issue or the diverter that is not moving properly. Thanks for any advice.
  • dryfly321dryfly321 Posts: 2
    I had the same problem w/my f-350.Only defrost.The problem was vacuum oriented.It ended up being the pulse vacuum solenoid located on the pass. side wheel well.Thats where your vacuum is delivered from for the selector to work.
  • rman6rman6 Posts: 11
    has anyone else had trouble motorcraft heater cores in f150's. I had dealer replace mine last November. It went out again in December, then again in February, and finally last week. They checked for electrolosis the last two times, and tried to explain to me this morning that it still could be electrolosis. Just wanted to know if anyone else has had similar problems. The dealer said that they've checked around and I'm the only one, but how many heater cores have been replaced on 98 half tons in the last six months?
    I appreciate any feedback.
  • jddaddjddadd Posts: 1
    got in my truck today and no readout on panel. no ac. its hot in texas
  • i turn on my truck the defrosters go on high speed but everything is off, i put the ac on and defrosters stop but i have no speed on ac
  • Aside from the passenger window regulator going, which was $400.00 to replace, I have a problem with the temp control. AC never really gets cold and the heater never gets really warm. In addition, my cig. lighter doesn't work. When I try to run power (XM Radio) off the cig lighter plug I get intermittent power. Could the two be related ala electrical problem. Help.
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