Need help wiring electric fans....

[bryanw1968]

I got a dual fan setup and am attempting to install it right.
I've also got a 3-way switch and a relay to put inline also. I have a pretty good idea of how to do it but I'm not sure whether to make a ground loop or a positive loop. The switch will allow me to either have the fans completly off, controlled by the thermostat or on all the time. Any diagrams or advice would be greatly appreciated.

[72hotrod]

I don't really know if switching OFF the fans is necessary or practical; you could accidently switch them off by mistake. Might not be an issue, but what good is it? A manual switch to override the temp switch would be a good idea for cool down with the engine off, or if the temp switch went bad.

Also, you would be better off using 2 relays for 2 fans; in the event of a relay failure you would still have 1 fan. The blade connectors would also have less current load on them.

You could run an ignition switched hot wire to the relay coil positive so your key switch would have to be ON for the fans to work so it would be less likely to forget and run down your battery if you leave the manual override ON. Then the relay coil negative would connect to your thermal fan switch on the engine. Then one side of the manual override switch goes to the same relay coil negative as the thermal fan switch and the other side goes to ground. I don't know how that might change with a fan controller set-up, so you would need to have the instructions for the controller to figure that out.

I don't know which circuit protection scheme is best, so I just used fusible links to the relays. Seems like it should be adequate for meltdown protection, but it won't reset like a circuit breaker. Hopefully I will get good service out of my fans, relays, switches and wiring so if a link pops, it means it is time to change a wore out fan. Maybe someone else can chime in with more detailed specifics about circuit protection and other considerations. Good luck on your project.

[bryanw1968]

Originally Posted by 72hotrod

I don't really know if switching OFF the fans is necessary or practical; you could accidently switch them off by mistake. Might not be an issue, but what good is it? A manual switch to override the temp switch would be a good idea for cool down with the engine off, or if the temp switch went bad.

Also, you would be better off using 2 relays for 2 fans; in the event of a relay failure you would still have 1 fan. The blade connectors would also have less current load on them.

You could run an ignition switched hot wire to the relay coil positive so your key switch would have to be ON for the fans to work so it would be less likely to forget and run down your battery if you leave the manual override ON. Then the relay coil negative would connect to your thermal fan switch on the engine. Then one side of the manual override switch goes to the same relay coil negative as the thermal fan switch and the other side goes to ground. I don't know how that might change with a fan controller set-up, so you would need to have the instructions for the controller to figure that out.

I don't know which circuit protection scheme is best, so I just used fusible links to the relays. Seems like it should be adequate for meltdown protection, but it won't reset like a circuit breaker. Hopefully I will get good service out of my fans, relays, switches and wiring so if a link pops, it means it is time to change a wore out fan. Maybe someone else can chime in with more detailed specifics about circuit protection and other considerations. Good luck on your project.

Yah I wondered about having two relays but my performance shop I buy my stuff from said that I could get away with one. I propably should get a second relaty though......

Again, any diagrams would be helpful.
Thanks