I added a fan to the a/c condenser. I want it to come on when I turn the a/c on. cant I just wire the fan power wire to the power wire on the "on switch of the a/c?

 

No , you must use a relay to control the fan motor , trying to connect a fan motor (huge current draw) straight to the "on" switch of the AC (only meant to switch a smaller current) will result in the switch being vaporized , perhaps the first time you use it .

 

I ran it through the relay and its still not working. I have constant batt to terminal 30, 85 in a ground, 86 is hooked up to the a/c switch, and the fan is hooked to 87. the **** is a rotary ****. is that going to make a difference? it doesn't have power in/power out.

 

85 needs (ignition switched) +12v power, the hvac control for A/C grounds 86... you currently have a grounded 85 and 86 terminal.

 

so I have 85 and 86 reversed?

 

I ran it today and the fan did come on when the compressor came on. my wiring is good. its nice when stuff works. doesn't happen enough.