A while back when reading about setting up electric fans, someone posted something about installing a relay in the circuit. I've now got my hands on a fan and an adjustable thermostatic switch but no relay. Before setting this system up, I'd like to try to find a good relay to protect everything from an overload but I haven't been able ot find a good affordable relay. Can anyone point me in the right direction as to what exactly I should be looking for or at least where to start looking?

 

get a small bosch relay, ask a guy at the parts counter for a 4 prong one. 30amps should do it, unless your really running HD fans

 

I have 2 electric fans on my RAM (16' each) with 2 seperate Bosch relays (mine are 5 prong, but either 4/5 prong relays will work, should be less than $5). Like aim4squirrels said, they are cheap at any autoparts store. Then, wiring them up is simple...

When looking at the prong side, you will see a few numbers, here's how I wired mine:

85 - Ground
30 - 12V Constant (battery) Power
86 - 12V Switched source (turns on when ignition is on, have to find a source of your choice)
87 - Out to your fan(s)

Remember this is the way I did mine, not necessarily the gospel truth, everyone has their own preference.

Also remember to put fuses somewhere in the system to prevent any major issues. I am running 15 amp fuses on the "out" side of my relays (between relay and fan) as well as between the 12V switched source and my toggle switches for my fans. Cheap protection.

Good Luck!