sstrickstein

I've recently done a radiator repair. I've got a 84 928s. Is the a/c fan on front of the radiator supposed to push air out the grill and the front of the car?. Mine does. I think this is weird. It wouldn't be a big deal to switch the wires but they are all stock. Im always learning about my car.

FredR

I thought your model year had a viscous coupled mechanical fan only?

Either way I cannot imagine Porsche installing an electric fan trying to push air into the incoming stream. It would be a bit like trying to take a leak on the bow of a ship pointing forwards!

Regards

Fred

sstrickstein

The clutch fan WAS on the inside. I replaced it with the 928motorsports kit. But these had an electric auxiliary fan on the front

MainePorsche

The radiator will cool the fluid running through it by conduction/convection. Conduction of the heat of the fluid to the metal of the radiator. Convection of the heated metal of the radiator to the environment. Relatively cooler environmental air (relative to warmer circum. engine air) passing actively and/or passively OVER the radiator will cool best.
Reverse the polarity so your fan blows over the radiator.

FredR

If the fan is on the front of the radiator then I would expect it should be designed as a pusher fan and the air flow should be through the radiator. As the motor is DC operated it will spin back to front if the terminals are the wrong way round for whatever reason.

Arguably it would still do its main job to some [very poor?] extent which is to cool when static or in slow moving traffic. Once you get moving the air blast will overwhelm the fan but it would be an absurd proposition I would think never mind inefficient.

I'd check your installation with Carl- I am pretty sure what you have "as installed" is not correct.

Regards

Fred

Carl Fausett

It's a DC fan motor. If you wire it backwards, it turns the wrong way. Try exchanging the wires around and see if it doesn't "push" air through the radiator like we want.

Randy V

Your fan direction is reversed.

sstrickstein

My front fan is the factory one. What would cause it to turn backwards if its not wired wrong?

auzivision

Pusher fans are tricky because some air get's reflected by the radiator. Short tell tails (1 inch long pieces of yarn) tied to a screw driver not held too close to the rotating fan will help determine actual direction.

Closer to the center of the fan it should draw toward it (pushing through radiator); yet at the same time, sometimes toward the perimeter on the fan you'll find air traveling the opposite way (reflected).

So what you may be feeling is reflected air if your fan is correctly wired.

MainePorsche

Kurt,
Good point.

LT Texan

Maybe the battery is hooked up backwards????

FredR

Still a bit confused what you mean by factory one- edit- I now understand what you mean. I would have thought Porsche would never fit a pusher fan notwithstanding your model had a mechanically driven fan as stock.

A pusher fan is a compromise- something you do if you have no choice. It is much more likely to induce recirculation currents which Kurt has rightly identified as possibly giving an impression of blowing the wrong way. If possible make sure what you think is happening is the case by dismounting the fan and run it up as wired- just make sure you do not get your pinkies caught in the fan! Just dangle a 1/2 inch strip of paper in front of the fan to test the deflection.

Regards

Fred

j.kenzie@sbcglobal.net

My 84 US has a pusher fan in the front of the radiator, and a viscous clutch driven fan behind the radiator. I once was experimenting with upgrades to the pusher fan. At one point I wired it backwards and it acted as an obstruction by fighting against the main fan. My engine went to overheat until I figured it out. You should be able to tell which way it should be turning by looking at the angle of the straight fan blades.
Good luck,
Dave

Dave928S

Here is a snip of the PET diagram of the A/C fan in question, which is a pusher fan through the A/C condensor in front of the radiator. The main radiator has a viscous fan behind which pulls air through.

If you see no alteration of the fan plug and socket then it may be wired correctly there, but perhaps might be reversed further up the line, such as at the actuating solenoid, or elsewhere.

Check the fan direction of rotation when going, and if not correct to push air through the condensor, then you have a reversal of connections somewhere which you need to trace.

When not assisted greatly by speed of travel, and the behind the radiator puller fan, it's possible that you can get air going through the condensor and taking the easy way out by spilling out behind the condensor in front of the radiator ... in that situation it'll be still cooling the A/C condensor but just not transferring all that heat through to the radiator behind. This is what you might be seeing ... if fan rotation is correct.

The Fixer

Your fan in reverse is slowing you down