I have one of those dual fan setups, where one fan is powered and the other fan is driven off a belt, so there's only two wires to deal with. I'm trying to use this fan setup on a GMC Sonoma V8 conversion truck I have, but have not been able to get these fans to come on. I have a 30A relay with a 20A inline fuse, trying to go thru a switch in the cab. I for the life of me cannot get these fans to come on.

There is a black wire and a brown wire coming off the one fan, so I'm assuming black is ground and brown is power? On the relay, the fused wire goes to battery positive, another wire goes to fan power (brown wire?), and the other wire goes to the switch. When I toggle the switch to ON, the LED lights up so I know the switch is getting power, but the fans don't come on. I have no automotive electrical knowledge, but I'm thinking the problem is with the fan. Am I missing a component that's supposed to make these fans come on? All I want them to do is turn on via the switch in the cab, no variable speed, no temp control, etc., so I thought just wiring them up thru a relay would make them come on?

If I can't get these dual MBZ fans to work, I'm seriously thinking of just getting two separate 11" fans, running them thru dual relays, to the switch, and be done with it. Worst case scenario is I have a switch for each fan, but I can deal with that.

So why won't these dual MBZ fans come on?!