[Pampered-Z]

To answer your question, it there a way without hacking the factory harness.

Maybe, Jet technology and Hypertech use to sell manual fan switch kits. Been a while, I think they were about $100, which is why everyone just started building their own. The Kit is basically a connector that fits into the harness, you then mount the switch and attach the ground wire.

BTW, building your own isn't that involved and you really won't be "hacking" the harness in that it's not allot of cutting and such, you just need to peal off a bit of the covering. From the EMC a green (primary) and blue (secondary) wires run to the fan relays. You will need to look at a shop manual for the pin outs. All you need to do it tap into either or both, then run a wire to a switch, and the the switch to a ground. Since you're working on the ground side you don't need to worry about adding additional relays. The fan will operator as factory until you flip the switch. If the AC is removed but the switch in still in the dash maybe all you need to do it jumped the wires that ran to the compressor to make a manual fan switch using that?

Also, what WildBillyT was asking about is because the car shouldn't run that hot at idle, the fan switch is more of a bandaid for what could be a bigger problem. You might want to go over the entire cooling system, flush, check hoses, temp sensor, thermostat etc.