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Wiring AC fan and Radiator fan on the same wiring?

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16g-95gsx

20+ Year Contributor
271
1
Nov 17, 2002
Christiansburg, Virginia
Just curious what I would need to do this. I have a SPAL slim AC fan, and would like to wire it up so that it comes on at the same time as my stock Radiator fan. Can I safely just wire it up into the stock radiator wiring so that it runs in parallel with the radiator fan wiring without anything additional?
 
Man, you are in luck. I just finished a "RAD FAN MOD" today to help cool down my radiator. Since the weather has started to warm up this past week (around 80*+) my car has been running hotter than normal. Between 209* and 216*. I thought upgrading from the stock Rad to a CSF rad would help with cooling since I already have a new 180* Tstat and new Rad Cap and Water pump. Also since I bought the ExtremePSI 1G FMIC (not installed yet) I thought it would be a good time to install the Spal Slim fan that came with it on the new Rad. I also bought a second slim fan to replace the stock passenger side rad fan. After all this was installed and wired up correctly my car ran even HOTTER!! 216* to 230* I was like WTF
After reading more posts than I care to count, about overheating problems with DSM's, most answers pointed to the obvious, Tstat, rad cap, or Water pump. All three of mine were/are new including the new Rad and Fans just installed. Still I had my little delemia. I figured my problem was due to the loss of the stock fan shrouds pulling cool air thru the entire rad core. The new slim fans leave alot of rad core un covered creating hot spots and reduced cooling. Then a light came on over my head, jump a wire to the AC fan from the rad fan so they both run when the car gets to operating temp. I tested the wiring on both fans to find the +leads, then I ran the yellow wire in the pic below from the Rad fan to the AC fan. BADA BING It works perfectly and took all of 5 minutes to do. My car now runs at 186* to 199* in 80*+ weather. Also the AC fan still works just like normal when i need the AC on.

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Nice. Yea thats exactly how I plan to do mine. However there are 4 wires on the radiator fan wiring, which 2 do I choose. I assume there are seperate ones for the speeds of the fan, however which ones are the max speed wires? And these wires can safely support this kinda current?
 
Its kinda hard to tell but I used the power wire that leads into the AC fan bypassing the HI-LO fan resistor. The jumble of wires on the right side of my pic are where my AC HI/LO resistor is, I just spliced my yellow wire into the single + power wire going into the fan housing. (it is red in my pic) I used 14ga wire and the current draw will not be a problem.
 
Not quite sure what you mean. There are 4 wires on the Rad fan, and 4 on the AC fan. On the AC fan you basically have 2 sets of 2 wires, one for low, and one for high speed. I'm assuming you arent using these wires at all, since the fan should be running anyway. Instead I'm assuming you taped the power wire that comes from your AC fan into one of the power wires for the Rad fan wiring, and the same for the ground from the AC fan. However my guess is that the 4 wires on the rad fan harness are just like the AC fan, 2 sets of 2 wires, one for low speed, the other for high. Did you simply tap yours into the high speed pair, and if so what did they look like as I dont know which pair is which.
 
I'm sorry TURFNSURF but NO WAY would I butcher up my stock Fan wiring with those rinky-dink Non- Waterproof Splice Clamps for those undersized aftermarket fans - There is a far more elegant way to do this.
 
Well yea, I wouldnt do it ghetto fabulous style personally, I was more just trying to figure out the proper wiring for it, I always do things cleanly with shrink tubing electrical tape and wire loom when possible so for me thats not a problem. I just want to know the proper way to do this
 
16G-95GSX,

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Above is a pic of my old stock rad fan. Notice that there are ONLY 2 wires going into the fan motor. (yellow circle) I tapped into the blue +positive power wire to power the AC fan. The plug may have 4 wires in it but the only two you need to be concerned with are the Positive leads into each fan motor.

Buck, I agree there is a far better way to do it but when the engine bay is still hot and you need to use the car for the rest of the afternoon you "go Ghetto or don't go at all" The yellow wire will be soldered into place when the Rad comes out for the FMIC install.. By the way when the FMIC does go in, im planning on putting the stock rad fan back in and using the slim fan as a pusher on the AC core. Sound like a god idea?
 
Ah perfect, , makes sense now. Those two wires are going to recieve power regardless of the speed the fan is pushed at. Since yours is a 1g let me make sure mine is also wired the same way. If so it will be very easy. Not that it wasnt before, just obviously I would know the 2 wires to connect it to :).
 
AAAAHHHHHH so the 2g's have a different wiring setup into the fans. OK then the best advice i can offer is to test for power on each wire out of the rad fan when it is on only. Make sure your AC is off. that way you'll know what wire to tap to draw power from, then into the AC fan. Then run the AC on low to trigger only the low-speed fan wire and test to see wich AC wire is positive. Do the same for the high-speed setting and wire. Then you'll know what wire to tie into, to power the fan at high speed from the rad fan power wire.. Hope that all made sense.

Good luck with the wiring and sorry for the confusion between the 1G's wiring and 2G's.
 
"TURFNSURF: BTW when the FMIC does go in, im planning on putting the stock rad fan back in and using the slim fan as a pusher on the AC core. Sound like a god idea?"

Absolutely - & I fully understand that you had to have a ride - I wasn't flaming & didn't use the "G" word. :thumb:
 
So when wiring BOTH fans to come on high speed, where do the fan motors draw the current from? I dont want to just jumper wires over to the next fan because of current draw and engine bay fires.
 
Fans are powered from the Fan Relays on Passenger side Fender well - Relays are powered by AC Switch in Dash & Temp Switch at lower Passenger side of Radiator.
 
Fans are powered from the Fan Relays on Passenger side Fender well - Relays are powered by AC Switch in Dash & Temp Switch at lower Passenger side of Radiator.

Can the relays handle the current draw of two fans in parallel the way you plan to wire them up? I like the idea of using a seperate relay for another fan to keep from overloading things.
 
Can the relays handle the current draw of two fans in parallel the way you plan to wire them up? I like the idea of using a seperate relay for another fan to keep from overloading things.
Yes, they will handle it just fine. I've had my SPAL's wired like this since 2005 and have had zero issues.
 
Where do the fans themselves actually draw the power from? I understand a relay is just a coil/electromagnetic switch that just closes the circuit.
Am I making any sense at all?
 
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