I would not recommend wiring the fan to a switch because if you aren't paying attention or just plain forget serious engine damage can happen very quickly.
I would instead suggest and it will be much easier to wire the fan to a thermal switch. Here is how:
The hardest part of this will be finding a thermal switch that will fit the threads on the head. You don't have an application so you basically have to walk in and ask for one based on size and hope you get a good parts guy that can do it.
What you need to do is replace the current sending unit with a 180 degree switch. Please note if there is another plugged off port on the head, pull the plug and put it there. If there isn't you will have to use the port its in now but you may have other issues because the fan isn't the only thing the ECM uses that info for.
To wire it up you will need a fan relay, a 180 degree switch, a 20 amp inline fuse and some wire.
Install the thermal switch and run a 14 ga. Wire from that to the trigger on the relay. The other side of the trigger on the relay goes to ground. (14 ga. Also) then find a power source that can run 20 amps. A bus tie or right to the battery is best. Then run a 10 ga. Wire from there to the load side of the relay. The other load terminal (10 ga. Also) goes to the fan and the other wire on the fan goes to ground. The 20 amp inline fuse goes between the relay and fan.
If you insist or have to use a switch then follow the above and change the wire from the thermal switch to one leg of your switch, and the other leg of the switch will go to a power source. The trigger side of the relay should be 14 ga. And the load side 10 ga.
Any issues just come back and ask.
Rich
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Wednesday, March 11th, 2020 AT 11:27 AM
