Well I'm 100% certain it's the switch.
I made a little jumper hose with two small metal tubes on each end.
With the system completely hooked up and the engine running I unplugged the switch. Using my new little tool I plugged into the green hose and white hose and the air grabber opened, then green to black and it closed, so I pretty much know it's the switch.
I bought it a year ago, but the company I bought it from said they will send a new one free of charge...