The reason I am gonna use this setup is for hands free automation. 1st stage on the VW switch activates the low speed on the fan, 2nd stage activates the high speed. This particular switch was designed to run TWO fans though, so when high kicks in, low is till active. This would detroy the fan motor if wired with traditional relays. That where the Volvo relay comes in. When low I triggered, it turns the fan on low peed. When high is truggered, even though low I still active at the VW switch, it SWITCHES inside the Volvo relay to high side only, effective acting as a 2 speed controller. This means that I don't have to manually hit a switch to toggle high or low on the fan, giving me a cooling fan sytem that operates like it would in factory designed system