You can wire it in with, or without the resistor pack. See this thread:
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Quoting GSTwithPSI:
For the 12v wire on your fan, connect the power wire to the fan directly to the battery.
Then, splice the ground wire of the fan into the blue wire with white tracer located on pin 4 of connector A-29. Everything you need to do so is in the post below. Make sure you use the links provided within. Again, this is the most simple way. There are tons of variables here, especially since I'm not sure what has already been screwed with in your wiring harness. With a properly functioning stock fan system, the way I outlined above is the easiest/best way in absence of the resistor packs. Let me know if you have any other questions.
About the toggle switch, that's not a great idea. You would need to wire in a relay, which is more involved than doing what I outlined above. Bottom line, you can't just wire a switch straight into the fan circuit.
Quoting GSTwithPSI:
The resistor on the cooling fan allows it to operate at 2 speeds. In the stock configuration, the cooling fan uses a low and a high speed relay.
The low speed relay is activated by the thermo sensor located at the bottom of the radiator just below the cooling fan. When the thermo sensor sees 185 degrees, it completes a path to ground for the low speed fan relay and activates it. The low speed relay then supplies the fan motor with a path to ground through the resistor, causing the motor to turn at low speed.
The high speed relay is activated by the engine coolant temperature switch which is located on the water neck. When the switch sees 215 degrees, it completes a path directly to ground, bypassing the resistor. This allows the fan motor to turn at full speed.
The easiest way to test the fan circuit is to jump the terminals that plug into the thermo sensor located at the bottom of the radiator. With the ignition key in the ON position, unplug the connector and jump the terminals together with a wire or something. This will simulate the thermo (fan) switch operating. The fan should kick on. If it doesn't, you probably have a wiring issue.
See these threads:
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Here's the diagram: