Need help wiring up two electric fans

[Destructo]

Alright, i'm basically re-wiring the fan on my truck since I just added another 10" aux. fan.

I'm going to be getting two 30 amp automotive relays, one for each fan. Have on/off switch for each fan and a thermostat for the main 16" fan. Also have inline fuse blocks to go in-line, will I need the fuses since I will have relays in the line? I have 10 guage wire to do this with also.

I want to run one 10 guage wire from the battery into the cab then split it to the 2 switches and pipe those two seperate wires to the relays and then to the fans. The wires will be pretty long, especially from the battery to the switches since the wires will go in on the driver side of cab and the battery is on the passenger side.

[NeCrOmAnCeR]

You shouldn't need 10 guage wire to the switches. The current flowing through the switches to the relays is very small. I'd use 16 or 18. Heavy wire from the battery to the switching contacts and then to the fans. Yes, I'd put an in-line fuse on the heavy wire, and get the voltage for the switches from a fused and ignition switched plug on the fuse box.

[Destructo]

The relay has 4 leads right? I know one is ground and one is power in, and does it have two other power spots for a switched connection right?

So it would go like this

1: heavy wire (10ga) to the relay direct from battery with a in-line fuse.
2: then run power from the fuse block in the cab to my switch and then from the switch to one switched side of relay and then out the other side to the fan.

Does that sound right?

[RockHQ]

Didn't really catch what you were after for, but a standard relay has 4 connectors with these numbers stamped next to them:

30: Continuous input (usually positive, always hot from battery etc but can be negative or ground too)
87: Switched output
85: Actuating coil negative or ground
86:Actuating coil positive

If you were to wire in a relay controlled fan, you'd:
-Connect 30 to your truck's battery with an inline fuse rated at the startup peak current +5 amps of the fan. Heavy wire here.

-Connect 87 to the fan's positive terminal. Heavy wire.

-Connect the negative or ground terminal of the fan to a suitable grounding point in the chassis. Some older fans with all-metal construction grounded from their body, so they had only an insulated positive terminal.

-Connect 85 from the relay to ground (any wire will do here, minimal current)

-Connect 86 to your fan switch, run positive to the switch from whereever you want, minimal current here too. Your truck's fuse block is a good source for +12 volts with no serious current requirements.

[Destructo]

I'm gonna get me two automotive relays from radio shack tomorrow and start wiring them up, I had to get a bigger alternator so I could run two fans. The stupid thing only had a 37 amp on it, its got a 73 now though.