Why A/C changes from Vent to Defrost???
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Why A/C changes from Vent to Defrost???
hello ya'll, my 92, 5.0, is having weird A/C problems. while driving, with the fan switch on Max A/C, the air flow switches back and forth from the vents (right) to the defrost vents (wrong). it seems to relate to how hard the engine is working. in other words, if it is idleing, air comes out the correct vents. if you are accelerating, or just keeping speed up hills on the highway, it changes to the defrost vents. i located the little vacum operated plunger thing under the dash, with a blue tube connected to the back of it. i watched this thing with the truck idleing, with the fan switch 'off' the plunger is all the way back, i turn it to defrost, the plunger doesn't move, when i turn it to max a/c, it moves all the way forward. i would think that's correct, but i don't know. what now?
I know this is kinda long, but i thought i should say everything i tried in one post. i hope someone can help.
thanks,
dynamitedan
I know this is kinda long, but i thought i should say everything i tried in one post. i hope someone can help.
thanks,
dynamitedan
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i tried to follow the little blue tube connected to the plunger thing. it went up under the dash, back out, through a connection (with lots of little tubes of all colors) then back under the dash, and outta sight. so i don't know where it goes. i'll look at all the lines around the coffee can looking thing this evening, could the can itself be leaking?
i really appreciate all the help!
dynamitedan
i really appreciate all the help!
dynamitedan
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Post Fiend
Joined: May 2004
Posts: 11,289
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From: Lakewood, Ohio
yes it could be leaking.
take everything out of glovebox, press on sides and remove it.
now you can see where the line goes.
take everything out of glovebox, press on sides and remove it.
now you can see where the line goes.
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Junior User
Joined: Jul 2006
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From: NE NC
I just went thru this same problem on my 93 302. It is the white vacuum line under the hood near the passenger side firewall on top of the blower motor. This controls your recirc door and what happens is when you have it on max A/C, it is supposed to close. If there is a vacuum leak it wont, and it will cause it to loose vacuum to the other doors, and the default on the vehicles with no vacuum the defrost works. Its a safety thing.
Senior User
Joined: Jul 2003
Posts: 431
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From: Hampton,Va
It never ceases to amaze how much this site helps people , just by reading this thread I fixed my Max A/C , it never blew harder than the normal setting did.I popped the hood and there it was, a dry rotted white hose, I fixed the trouble area using some hose I had laying around , and WOW! It blows harder now and doesn't cut off when accelerating, I always thought the motor shut the A/C off to save power for accelerations. Thanks a million!
Mike
Mike
Senior User
Joined: Apr 2005
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Many vehicles remove power to the A/C clutch to give a bit more horse power under pretty firm acceleration demands... Used to tick me off plenty as I was USUALLY pretty far into the power band of four banger engines in company vehicles...
Brent
Brent
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awesome! that was it... thanks guys. but, for some reason, someone before me put a cable tie around the plunger thing that sits ontop of the blower, keeping the arm squeezed in... i cut it off, and it seems to work fine... it was rigged up to keep it in the Max A/C (recirculate?) position all the time. weird...
anyway, thanks for the help.................this place does rock!
dynamitedan
anyway, thanks for the help.................this place does rock!
dynamitedan
Lead Driver
Joined: Feb 2003
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From: Oak Harbor, OH
Originally Posted by dynamitedan
awesome! that was it... thanks guys. but, for some reason, someone before me put a cable tie around the plunger thing that sits ontop of the blower, keeping the arm squeezed in... i cut it off, and it seems to work fine... it was rigged up to keep it in the Max A/C (recirculate?) position all the time. weird...
anyway, thanks for the help.................this place does rock!
dynamitedan
anyway, thanks for the help.................this place does rock!
dynamitedan
You might not get heat now then in the winter. This is a common problem when the truck doesn't warm up much. The outside air is cool enough to cool the heater core down to where it can't heat the cab.