Using AC fan wiring for main cooling fan

#1

I know this topic has been beat to death on most forums but I’m slightly confused/don’t know what to try next.

I have this fan http://www.jegs.com/i/QuickCar+Racing/635/60-034/10002/-1 and wired it to the AC fan wiring harness with the resistor for high/low operation.

Fan wouldn’t turn on when the AC button was pushed.
Wasn’t able to leave the car running long enough to see if the sensor in the radiator would kick it on.

So to test the fan wiring, I jumpered the plug for that sensor. High and low operation worked. Noticed the fan was blowing the wrong direction so I reversed the 2 wires coming from the fan. Now jumpering the plug doesn’t work. Switched the wiring back to how it was, still no worky.

While jumpering, I hear a buzzing kind of noise from the relays in the engine bay fuse box. I switched out all relays and #19 & 18 fuses. Didn’t change the buzzing and still no fan blowing.

Could I be correct in thinking that it’s the resistor from the AC fan wiring?

Sorry if this doesn’t make sense. Been a long day.

#2

That’s the aux fan. Using it as a cooling fan is common but most folks just run a 30A switch to it. If you want, you can wire in a relay so you can use a smaller switch, but that adds complexity. It sounds like you’re trying to make it even more complex yet. Heck with trying to use the OEM relays, just wire a big switch to it and be done.

#3

This is what I coppied:
http://www.r3vlimited.com/board/showthread.php?t=134232&page=4
(See post #57)

If I knew what size resistor was on the ac (aux) fan wire harness, I would just try testing out a new one.

I’m going to try bypassing the diode under the fuse box 1st.

#4

I was running something similar, except I substituted a toggle switch to turn it on. Never could get the low speed to work… Course, I am using the stock AUX fan, and my existing wiring was pretty chopped up to begin with.

Ended up having to hard wire the fan to always on because for some reason the 12v to the switch died. I was too tired to investigate further, and with probably just wire a separate relay and switch for simplicity sake. Would trust my wiring over 25+ year old copper during a race.

#5

It works! A plug was loose.
My fan now turns on low when the temp sensor in the radiator triggers it and turns on high when I push the AC button.

If your original wiring is in good condition, this is a super easy way to install a new fan cleanly.

#6

Yep. I have had mine wired up to run high speed when the temp sensor tells it to kick on and it has been working flawlessly for years.