a/c stuck on defrost - Ford Powerstroke Diesel Forum
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post #1 of 3 Old 08-21-2013, 07:12 PM Thread Starter
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a/c stuck on defrost

I am new to the sight and first time diesel owner 02 f250 7.3 crew cab 8ft bed, 122k with an 4r100. The truck is blowing air through the defrost vents with heat or a/c. I can adjust the temp no problem. The knob for air direction, vent, a/c, max a/c, off, works fine. I have looked online and this seems to be a problem with these trucks. The vacuum pump does come on and stays on as long the truck is on and does not turn off. Also there seems to be a tie between this problem and 4x4 auto hubs. I have manual locking hubs. I pulled the black hose off the solenoid and plugged it with my finger and the pump shut off. Seems to be a leak somewhere. That's my next move this weekend. I don't have the EATC, just old fashioned manual knobs for climate control. What do you think. Thanks for the help.
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post #2 of 3 Old 08-21-2013, 07:20 PM
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you have a vacuum leak, the pump shuts off when you plug the hose , means you have a leak at the hub or somewhere down line from the solenoid. the ac goes to defrost because you have no vacuum to hold the blend door shut to divert the air to the other vents. fix the vac leak and that will solve the problem

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post #3 of 3 Old 08-21-2013, 07:28 PM
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Unplug relay on pass. inner fender until you fix leak.
This will also help find problem, if vent work ok, leak is in 4x4 areas.
If vents still don't work then problem is somewhere else.
Check hub selector mine corroded out at the center part of selector.
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