That would be too easy. I was hoping for that same thing but I checked my pressure switch power and it not only was 220v but it was only powered when switched off. In other words no power to the switch when the compressor is running.
That seems very odd. Is it a common pressure switch that switches the power in, on it's way to the motor. Mine is a simple setup and the line in is hot all of the time (when the circuit to the compressor is switched on from inside the garage) and then when the pressure gets low the contacts close and the motor gets power.
Mine has two 120v hot legs into the switch which gives 240v. You could use one hot leg to power a fan, but the load would not be balanced on the switch and you would need a neutral or ground (if they are bonded in the panel). It isn't proper to use the ground wire as a neutral, but not everyone follows the rules.
Thanks. Seems like a bunch of hassle to get 12VDC fans running. Think I am just going to go for a low-current 220v fan and piggyback onto the 220v compressor motor.
This is how I would go about it. I did the same when I setup my TIG cooler. It wasn't hard to find a 220v fan.
I bought a fan for an aftercooler, but never bought the B&M cooler. The fan might be 120v, IIRC. That compressor gave up so I need to replace it first. Right now a 5hp SB 80 gal is my first choice.
The thought of putting a homemade cooler on a $2500 compressor seems odd, but then again, they get around $600 for their aftercooler.