Dual fan wiring help - PeachParts Mercedes-Benz Forum

Frank Reiner · #1 10-21-2016, 06:45 PM

Quote:

Originally Posted by socal1200r

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?! (Fan_dual 11in MBZ_20160718_zpshovt0i3l.jpg Photo by socal1200r | Photobucket)

1) As you now know, brown is ground/negative, black is positive.
Using jumpers/test leads, connect the fan directly to battery: brown>neg., black>pos. Does the fan run?

2) Make a drawing of the wiring: fan, relay, battery, & switch. Scan & upload as a thumbnail to this thread.

socal1200r · #2 10-21-2016, 07:23 PM

You'll have to excuse my limited Paint skills, but this is a diagram of how I have these fans wired up:

Brown wire off the fan to relay power, black to ground. I now know that these have to be reversed.

Other relay red, with an inline 20A fuse, to battery positive.

Gray off relay to switch.

Black off switch to ground.

The switch is working fine, the LED goes on and off when I toggle the switch back and forth.

So if I switch the brown and black wires coming off the fan, they should turn on, even without the engine running or key turned on? Or does the engine have to be running because of the initial load when the fans start up?

socal1200r · #3 10-22-2016, 12:55 AM

Quote:

Originally Posted by Frank Reiner

1) As you now know, brown is ground/negative, black is positive.
Using jumpers/test leads, connect the fan directly to battery: brown>neg., black>pos. Does the fan run?

2) Make a drawing of the wiring: fan, relay, battery, & switch. Scan & upload as a thumbnail to this thread.

Here's an elementary school level depiction of my wiring diagram (you'll have to excuse my limited MS Paint skills, lol). I'm thinking there's only so many variations I can come up with to get these MBZ fans to work. If not, then I'll start from scratch with two separate 11" pusher fans, two 30A relays, and run them into the one switch.

As far as I know, the only thing wrong in the diagram is the brown and black wires coming off the fan have to be switched, since brown is ground and black is power. When I go to test them again, I'll use some jumper wires and ground the metal fan shroud as well, just in case...