I got a 91 rs camaro that was a tbi car that cam with the single factory fan eliminated the factory fan and installed a flexalite black magic fan. Trying to figure out which wire I hook up to the “c” terminal on the fan. It’s saying to hook up to the positive wire that triggers the ac compressor.

 

'C' would be tied to the green wire on the A/C clutch.

 

Another option would be to tie it into the positive wire on the A/C pressure cycling switch. Here is a PIC of the switch.



If you connect it to the green wire off the compressor you will only have power running the fan when the a/c clutch cycles on. This would result in a constant on/off of your fan, sometimes multiple times per minute. This would work to move air across the condenser when the compressor is running, but in my opinion not as effective as constant air flow to keep it cool.

By connecting it to the constant power wire at the A/C pressure switch (located under the hood on passenger side, attached to metal hoses coming out of the evaporator box) your fan will run constantly any time the A/C circuit is powered. Basically, when you turn your dash switch to any of the A/C positions OR defrost the fan will run to keep your condenser cool. The pressure switch has two wires. One wire is constantly hot whenever the dash switch is in an A/C use position. The other wire is only hot when the pressure switch closes (activates), sending power to the A/C compressor clutch to activate the compressor. This is the green wire running to the compressor. It is easy to figure out which wire you want. Turn the ignition ON but leave the engine OFF, turn the dash A/C selector on max A/C, remove the wire plug from the A/C pressure switch under the hood, then connect a probe light or multimeter to check each terminal on the plug itself. The one that is hot (12+ volts of power) is the wire that will run the fan constantly anytime the A/C system is turned on inside the car. The other wire is only hot when the A/C clutch is cycled on.

I did this on my Camaro and my wife's Camaro. I used the constant power wire to run the electric fans whenever A/C is switched on. A/C blows much cooler in the summer with a fan pulling air across the condenser. It also lowered my A/C pressures and eliminated some secondary issues from the previously too-high pressure. Either wire hookup will work for you though. I am interested in feedback from people who have used the green wire off the compressor, since I have never actually powered it off the compressor wire and have always used the constant power pressure switch wire. Even with the compressor wire hookup I think you would see almost constant running of the compressor at idle during hot weather, which means your fan would be running almost constantly anyway. During cooler times or at highway speed the electric fan would cycle on/off more frequently in response to the A/C clutch cycling, which would probably work just fine since the cooler weather and highway speeds shouldn't require the constant running of an electric fan anyway.

Not sure why you removed the factory fan, but my experience with the Black Magic vs factory fan shows the factory fan system worked better (assuming all other original components are in place and working correctly). I have NOT had good luck cooling with the aftermarket fans like Black Magic, but my experience is with the s-shaped blades and NOT the straighter blade fans which are also available from Black Magic and other companies. The s-curve blade fans don't seem to move as much air or pull air as well as a straighter blade.