Radiator Fan Wiring

[ThickCobra]

I installed the Breeze radiator shroud and their manually adjustable thermostat, which is installed inside the shroud, with an external adjustment knob. I used the RF fan wire in the front harness to wire the fan. If I decide to place a fan switch on the dash, to override the thermostat, if necessary, will I have to run wiring from the dash out to the fan? Or, is there an easier way to do it. My concern is the in-shroud thermostat is the power switch. How do I override this when I want to run the fan continuously?

[Polecat]

I don't have my kit yet however I am a controls engineer by trade so I would say you have to splice in the dash switch 12V wiring after the thermostat output at the fan. I am not familiar with the design but if there is not enough exposed wire to do this you would have to create a simulated overheat voltage signal and over ride the thermostat signal but this can be complicated so the first option is by far the best.

Good Luck!

[Gumball]

Jay - I"ll try to get over to my workshop tonight and scan my wiring diagram for you. As you saw, I have both the thermostatically operated switch (the one with the probe in the radiator fins) and an override switch. If I remember correctly, it was Jeff Kleiner who put me on the path to the correct wiring for that set-up.

[edwardb]

The RF harness that I received with #8674 one year ago is different than the RF harness I received with #7750 a couple years before. (1) The cooling fan circuit is now a battery circuit. Previously it was an ignition circuit, and would only run when the ignition switch was on. (2) The newer harness also doesn't have any of the cooling fan/switch wires in the dash harness. So some of the advice from the past needs to be modified because the harness has definitely changed. Also explains some of the confusion some have had trying to follow advice from the past. I've received a couple PM's on this exact point. Everything below assumes this is the more recent version of the RF harness.

In your front harness there are three fan wires: +12V fan power, ground, and DK GRN - FAN THERMO SWITCH. When the fan thermo switch is connected to ground, the fan relay is energized and +12V on the fan power wire runs the fan. I'm assuming the fan thermo switch wire is the one you have going to the adjustable thermostat and it's going to ground to run the fan. There's another DK GRN - FAN THERMO SWITCH wire in the sending unit harness. Check the RF schematic. They're the same wires Y'd together. You can pull this wire out of the sending unit harness and route it to a dash switch. Wire on one side of the switch, the other side to ground. The manual override switch now does the same thing as the thermo switch and can be used to run the fan whenever you want.

Some also like an indicator light. I do. That was easier on the old harness with the wires in the dash harness. Now you need to run a new wire in parallel from the +12V fan power wire to the plus side of an indicator light. The other side to ground. 12 volts on the fan will also light the indicator. You could get a little more creative and tap into the +12V at the relay in the RF fuse panel. Same thing.

Just be aware, again if this is the newer harness which I assume it is, this is a battery circuit and if either your thermo switch or manual override switch is on, the fan will run even with the ignition off. Some want it to work this way. If you don't, there's more work to do. For my current Coyote build because the Coyote harness and PCM/PDB control and power the cooling fan the RF harness components are not used. I did however use the RF cooling fan circuit for my aux power plugs under the dash. I added a relay that connects the DK GRN - FAN THERMO SWITCH wire to ground only when the ignition switch is on. That way the circuit becomes an ignition circuit, and the aux power plugs are only on when the key is on. Something similar could be done with it as an actual cooling fan circuit.

Hope this makes sense and helps.