so my 14 JKU M-380 is 100% 'de-computerized' - all of the factory wiring and computers are deleted and instead uses a Painless Performance wiring harness, and it's awesome. But, I'd like to use the OE engine cooling fan/shroud, but I don't know if the OE wiring setup can be 'controlled' by an aftermarket fan controller, specifically my Sniper EFI harness. The Sniper harness has two output wires (low/high) which can be wired to a 2 speed fan (via relays), and while I think the OE fan is a 'variable speed' unit I do not know if the OE fan can be wired to function as a 2-speed unit.

The factory setup has three wires: Power, Ground, and Pulse Width Modulation, and I don't think(?) I can wire up an OE fan assembly in the old-school manner?

AFAIK, this is the wiring breakdown for the OE fan setup:

• Red (or Positive Power): Supplies 12-volt DC power to the fan motor.
• Black (or Ground): Provides the ground connection for the motor.
• Green (or Signal/Control Wire): This wire carries a Pulse Width Modulation (PWM) signal (typically 9v-12v) from the computer (TIPM) to control the speed of the fan.

The 2-speed aftermarket fan I'm looking at has three wires:

• Black (Ground)
• Grey (Low speed 12v)
• Brown (High speed 12v)

Not sure if it's possible to re-wire this setup to function "old-school" and operate on a 2-speed setup. Anyone done it and/or know for sure? If not I'll just go with a big generic fan and fab a shroud...but I'd sure like to use the OE fan/shroud setup, if possible.

Thanks much,
- Sam

 

ok - thanks to my good friend George and his intimate knowledge of electronical voodoo, we think we figured out how to control the OE fan assembly without the OE computer. The OE fan setup uses a big power and ground wires, and a smaller 'signal' wire which uses Pulsed Width Modulation (PWM). If my info is correct, I can simulate the factory PWM signal with an aftermarket PWM controller, in my case two of them, which should activate the OE low speed fan at temp X (the controller is adjustable), and the high speed setting at temp Y. I'm running a Holley Sniper EFI, and it has two output (ground trigger) wires in the harness - one each for low and high-speed fan(s), meaning the Sniper is intended to operate two separate fans, which we think have a work-around for. Here's the diagram -
Low speed. 12v switched power goes to 86 on the Hi relay, and 30 on both. When the Hi relay is not in use post 87a is 'hot' and sends power to 86 on the Lo relay, powering the Lo relay, but it's not active because it's a ground trigger setup. At say 190* (programmable), the Sniper will ground the low-speed output, which will ground/activate the Lo relay, which will send 87 output to the Lo PWM controller, which will send PWM signal (low) to the fan for low-speed fan ops.

High speed. In my case, the Sniper is designed to operate two independent fans simultaneously - one for regular cooling and the second for 'more' cooling, meaning the Sniper does not deactivate the low speed output when the high-speed hits. So, we needed a way to disable the low-speed relay and allow the Sniper to have the low-speed output grounded to no harm. When things get hotter (say 220*), the Sniper will ground the high-speed output, which will ground the Hi relay, which will open 87a on the Hi relay, disabling the Lo relay, and simultaneously send 87 output to the Hi PWM controller (adjusted higher), which will send PWM signal (high) to the fan for high-speed fan ops. Because the relay is disabled there is no way for the PWM controller(s) to 'back-feed' into each other.

So it's not 'variable speed' like I think the OE setup is, but low and high speed should be pretty good, at least for me.

These are the PWM controllers - https://www.amazon.com/dp/B0BBFKWHB3?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1

Anyway, this'll help me get what I want - hope it helps someone else.

- Sam