Radiator Fan Direction and Wiring

Mitch Krause

Supporter
Hello,

I think I did enough research and reading to determine that the direction of the airflow through the radiator should be from front to back. In that case with my fans, that means that they are pulling air through the radiator. That is accomplished by putting the 12VDC signal into the black wire on the fan and grounding the blue wire on the fan. The black wire looks to be a 16 Gauge wire and the blue one looks to be 14 Gauge (it looks a little bigger). I ran the fan with it hooked up this way for a few minutes, and could not detect any warmth on the black wire, therefore my conclusion that even if the black wire is slightly smaller, I am OK sending the positive signal down that.

Am I missing anything, or any thoughts on this?
 

Randy V

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Not certain of this but I think the blue wire was positive. It is on my street rod fans anyway.
You can just hot-wire them to a car battery to test. Reverse polarity smiply runs the fan backward and will not harm anything.
The fans should be energized through a relay.
I did fit the fans and AC condenser on the radiator - did you disassemble?
 

Mitch Krause

Supporter
I did not disassemble anything. The blue wire was positive, but putting the 12V signal on that results in the fan pushing air through the radiator from back to front. Putting the 12V on the black wire results in the fan pulling air through the radiator from front to back. Thus the reason that I believe that the 12V should go to the black wire. Make sense?
 

Terry Oxandale

Skinny Man
Not sure why one wire is of heavier gauge than the other, being the same current flows through both of them. 16 gauge should be fine for even two fans (12" for example) in parallel off the same source wire, and certainly for one larger high-output fan.
 
Last edited:

Randy V

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I did not disassemble anything. The blue wire was positive, but putting the 12V signal on that results in the fan pushing air through the radiator from back to front. Putting the 12V on the black wire results in the fan pulling air through the radiator from front to back. Thus the reason that I believe that the 12V should go to the black wire. Make sense?

Makes perfect sense....
 
What about blade design? Are the blades made to efficiently move air in one direction? Do you have the make and part number so we can look it up? There should be a rating for fan draw, constant speed and startup. Some fans only draw about 5-6 amps each in steady state, some pull over 20 amps, thus the need for the 30 amp relays!
 

Mitch Krause

Supporter
Tom,

Unfortunately I don’t have a male and model. Maybe Randy recalls. From my view nothing really provides that info. I have attached the picture so you can see the blade design maybe that provides some thoughts. All I can say is that the fan seems to suck a piece of paper against it with about the same force/suction on each side depending on which way it is turning.

It is on relay circuits with the relay on the front power board about a foot from the fan.

The little sticker in the middle of the fan that says 12v has some hard to read numbers and letters on it that are nearly indecipherable I might try and see if I can make sense of them. I tried to get a rubbing with a pencil and paper but they are not deep enough for that.

Not sure if there is info on the other side of the fan I didn’t want to take it apart I will take another stab at the numbers.
 

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Randy V

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The fans look much like Deralle (sp) fans but were in plain white boxes.
They are PULL type fans and are mounted properly..
 
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