i've been using search to find answer but can't seem to find my answer using relay. Anyone know how to wire up aftermarket fans that have only two wires using relay? i have two relays, one for each fan. Thanks you....

 

Pretty simple.

A standard relay will have four terminals - some have five - in any case you only need four terminals.

There are two circuits - two paths of electricity that you need to set up.

The first is the power source for the aftermarket fans. The power comes from the battery, through a fuse (MOST IMPORTANT!!!!), to the armature of the relay (this is the part that moves), and then to the positive side of the fan (typically red but not always). The other wire from the fan is grounded.

The second circuit is the control circuit where power comes from a fuse box ignition controlled source, to one side of your SPST (single pole, single throw) switch, the other side of the switch will connect to the coil of the relay. The other side of the relay coil is grounded.

Here's how the circuit works. When power is on to the fuse box (key in the slot) and the accessories like the radio and dash board are lit up power is supplied to one side of your toggle switch. The voltage will "wait" there until you flip the switch. Power then flows out of the switch and into the relay's coil energizing it and turning the DC power into a magnetic field. That magnetic field attracts and pulls on the movable armature lowering it. Power from the battery is "waiting" on the relay's armature at all times so when the armature lowers it connects the battery to the fan causing it to start up.

Flipping the switch to off stops power energizing the coil, collapsing the magnetic field, and letting a tiny spring return the armature to it's normal resting position breaking power to the fans.

 

One wire from the fan motor goes to ground, and the other goes to a contact on the relay. A wire from the battery goes to the other contact on the relay. You should have a fuse on this wire as close to the battery as possible.

One side of the relay coil will go to ground, and the other side of the coil goes to your switch. The other side of the switch is connected to the same fuse as the fan motor.

 

Here's a drawing I made for the roof lights on my Xterra. Rather than connecting the relay to the driving lights you'll be connecting the fans in that part of the circuit. The schematic symbol above the word 'Ground' is the symbol for a DC ground like the frame of the car. I connected the switches to my battery so I could power the lights even with the truck off ... I would notice 500 watts worth of lights left on by accident so that's not a worry.

 

Thanks guys... i'll update after i get everything working....

 

anyone know which wire on the stock fan wiring harness is a low and high speed?? thinking about running one relay on both fans for low and second relay for high/AC. or not. either way i would like to know which is wire is for low and high/AC.

Thank you

 

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