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Old 12-29-2010, 10:02 PM
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Why Is a Pusher Fan Added for AC

I notice that most aftermarket AC installations have a pusher fan on the AC condenser that is placed in front of the radiator. If the main fan cools well, why is a pusher added? OEMs don't have pushers.

I have a Cooling Components 16 inch shrouded fan on my mild 350 engine. It keeps the engine at 190 in hot weather. The AC installer added a condenser and 12 inch pusher fan in front of the radiator. I disconnected the 12 inch pusher this summer and couldn't tell any difference in how hot the car ran or how cold the AC output was.

John

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Old 12-29-2010, 10:24 PM
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A/c Pusher

At Idle In The Heat Hook A High Pressure Gauge Up To The High Side Of The A/c And Get The Engine Hot ,turn On Air On High Without Pusher Fans,get A Reading...it Will Climb...see Where It Tops Out At, Then Turn The Pusher On And It Should Go Down....when You Travel Down The Road The Pusher Need Not Run...if It Does You Have To Install A Pressure Switch That Only Turns On When High Pressure Side Goes High.. They Can Be Found From Lots Of Modern Cars They Are 3 Wire Sensors Say On A 97 Malibu. Then Use That To Switch The Neg Side Of Relay Trigger To Turn The Pusher On... Have To Get A Sensor Diagram From---alldata Or Program Like That... If This Will Work For You I Have Alldata And Can E-mail You The Wiring Spec...if The High Pressure Never Goes Up Then Leave Them Off.....but You Have To Make Sure You Get It All Hot And Give It Time Idling For The Pressure To Raise,, With The Air On High And Blower On High... It's Been A While But Too High Is Somewhere Around 350-400psi The Cooler The Condenser The Better The Output And The Longer The Life Of The System... And Also Keep The Condenser Washed Clean...dirt That You Can't Even See In There Can Raise The Pressure As Much As 100psi...
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Old 12-30-2010, 06:46 AM
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Quote:
Originally Posted by JohnTN
I notice that most aftermarket AC installations have a pusher fan on the AC condenser that is placed in front of the radiator. If the main fan cools well, why is a pusher added? OEMs don't have pushers.
Like breakdown says if your AC does not get enough airflow the pressure will get to high in the system and damage it.

It costs far less to put an extra fan in than to keep testing to make sure your car has enough airflow. Also every car is different so instead of figuring out wiring for every car they do to use the original fan with AC they just run their own. Cost is a factor and most people won't pay the difference for that much extra work.

As far as OEMs not having pushers every OEM works a little differently. Some older cars Like Triumph TR7 had pushers because AC was more of an afterthought. Some cars have two puller fans side by side, one for AC and one for cooling the motor. Some cars like the PT Cruiser have one puller fan but two speeds on it. one speed just for ac and one for cooling the radiator. they are harder to troubleshoot and too expensive and complicated for aftermarket installs.
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Old 12-30-2010, 08:58 AM
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Quote:
Originally Posted by BREAKDOWN5
It's Been A While But Too High Is Somewhere Around 350-400psi The Cooler The Condenser The Better The Output And The Longer The Life Of The System... And Also Keep The Condenser Washed Clean...dirt That You Can't Even See In There Can Raise The Pressure As Much As 100psi...
Vintage Air Trinary switch cuts the compressor off at 406lbs.
The little GM R-4 compressor has a switch that cuts off in the 410 range.
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Old 12-30-2010, 11:06 AM
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Guess I will hook my pusher fan back up just to be safe.
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Old 12-30-2010, 04:27 PM
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I've seen stock pusher fans on some vehicles (a few BMW's for example) and its always a RWD vehicle with a an engine-driven clutch fan, with A/C that uses R134a.

On an R134a system that does not have enough condenser air flow the high pressure goes up and the high pressure cutoff eventually turns the compressor off. My best guess is they found that at idle the clutch fan does not move enough air through the condenser to keep A/C pressures low and cooling capacity high. R134a systems always have a high pressure safety cutoff switch, which was seldom found on R12 systems (apparently not needed).

Bruce
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