Air conditioner and acceleration

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Apr 15, 2002 | 11:49 AM

Pwalls

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Joined: Dec 2001

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From: Cordele USA

Air conditioner and acceleration

Cranked up the truck yesterday afternoon, turned on the AC and proceeded down the road. Immediately noticed a weird occurence. Whenever I accelerated, the AC quit blowing out of the front vents and started blowing out of the defroster vent. Did it by degrees. More acceleration gave more out of the defroster with sometimes all of the AC coming out of the defroster and none out of the front vents. In all cases, whenever I stopped accelerating, the AC went to normal and blew out of the front vents. Have never heard of this before. Will take it back to dealer later this week. Was hoping someone might have an idea as to what it might be. Thanks in advance for any help.

2001 Supercrew XLT 5.4L

May 16, 2002 | 03:49 PM

phxts

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Joined: May 2002

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From: Phoenix

Air conditioner and acceleration

Just had the same thing happen two days ago on my 98' F150 4x4. Today it has all gone to the defroster, still blowing cold but out of the wrong vents. If you learn anything please forward any info. My shop manuel has nothing in regards to vents, etc...

Thanks,
Tony

May 17, 2002 | 12:51 PM

Superbru

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Joined: Jan 2002

Posts: 351

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From: Delaware

Air conditioner and acceleration

You are experiencing a vacuum leak or failed vacuum motor. The AC and heater vents are controlled by vacuum motors that use vacuum to open them and spring tension to close them. So, if your vacuum drops, as it will under acceleration, the spring tension closes the vacuum motor and the cool air is diverted to the default area, which is the defrosters. Listen for a hissing sound under the dash. You may have a leaky hose or one that has come off the vacuum motor.

Bru
2002 F150 Super Crew
Black 4X4 Lariat
5.4 Engine Ford Chrome Bars

1979 Bronco 351M 75K orig.