COOLING FANS ???
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Joined: Dec 2006
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From: ms. gulf coast
Car: 91 R/S , 89 dodge p/u
Engine: L31 GM crate re-cammed , 318
Transmission: T-5 , 4 speed auto
Axle/Gears: 3.42 , ?
COOLING FANS ???
while doing a little cleaning and checking last week , I noticed my cooling fan came on when defrost selected . I know they should/do come on when A/C is selected . maybe I just never noticed before . does anyone know if they should come on when defrost selected ??? thanks in advance ...
Joined: May 2009
Posts: 384
Likes: 16
From: Des Moines IA
Car: 89 forrmula
Engine: 350 TBI
Transmission: T-5
Axle/Gears: 3.55
Re: COOLING FANS ???
If the compressor gets cycled (which it does when you select defrost mode) it triggers the fan relay. Newer vehicles usually use a trinary switch circuit in place of this method.
Thread Starter
Supreme Member
iTrader: (1)
Joined: Dec 2006
Posts: 2,403
Likes: 4
From: ms. gulf coast
Car: 91 R/S , 89 dodge p/u
Engine: L31 GM crate re-cammed , 318
Transmission: T-5 , 4 speed auto
Axle/Gears: 3.42 , ?
Re: COOLING FANS ???
thanks , never too old to learn (damn I'm old) . 
Joined: Dec 2005
Posts: 4,795
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From: St. Cloud, MN
Car: 1984 Trans Am
Engine: LS1383 in work
Transmission: Magnum F - to be installed
Axle/Gears: Zexel Torsen 3.73, 28-spline mosers
Re: COOLING FANS ???
My 84 turns the fan on when defrost is selected. /shrug
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Joined: Jan 2000
Posts: 3,178
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From: Tracy, CA
Car: '87 IROC
Engine: LB9
Transmission: TH700R4
Re: COOLING FANS ???
In defrost mode the AC compressor runs to provide de-humidified air if the outside temperature is above 40F. When the compressor is running the engine cooling fan(s) will run as well.
De-humidified air helps clear the inside of the windshield.
De-humidified air helps clear the inside of the windshield.
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