Fan not turning on

[Nilao]

The ecm supplies the ground. When you interrupted ground you de energize the solenoid allowing the air on the fan side to exhaust from the bottom.

Do not purchase a 2 port. All the have is an inlet and outlet. There is no way to vent the pressure on the fan hub without a exhaust port.

You want a 1/4" 3 port normally open pnuematic valve. Something like https://amzn.to/2LfwCXo