Wiring my fan

[Project240]

OK, the instructions for my FAL 12" radiator fan say to run one of the wires from the control box to a 12V power wire, *preferably one that won't cause the fan to run while the car is off.* My question is, can I run it to the main alternator power wire?? Alternators put out a 12V charge (right?) and they only put out the charge while the engine is running. Would that work fine??

[JonPowell]

do not run right to the alternator. Run it to a wire that has constant power like the white one in the plug that goes to the starter...wire that one direct to the sensor, then from the sensor to the fan. Whenever the sensor is hot enough to turn the fans on, they will run till the sensor cools down.

[Project240]

What sensor?? Could you maybe make that a little more clear, I'm not sure what you mean...

[JonPowell]

You are kidding, right? The thermo switch that tells the fans the engine is too hot and kicks them on. When you got your fans, they should have come with something like that. If your car was a SOHC car, then there was one in the lower radiator hose stock also

[Project240]

Well there's a sensor bulb that runs straight from the fan's control box (it's permanently attached). It's a copper wire with a bulb on the end that you run into the upper radiator outlet. I've run that already, the only thing left is this one wire.

My car was DOHC, but there is a wire with a plug on the end coming from the bottom of my radiator (I'm running the RB20 radiator) that is currently not connected to anything...

I knew you meant some sort of thermo sensor like that, but I was thrown off because, well, you can't really do anything with this sensor bulb that came with the fans besides stick it in the upper rad outlet....

[Project240]

We're kinda worried the ignition wire won't be able to carry that much electrical load with the 1200CFM fans running off it.

....but, barring that, since it has a bulb sensor permanently attached to the control box, should I just run said 12V power wire straight to the ignition switch wire, and let the bulb sensor do its thing???

[BoostFab]

We're kinda worried the ignition wire won't be able to carry that much electrical load with the 1200CFM fans running off it.

that's why the maker of those fans urge you to incorporate a relay into the setup. this way the constant power for the fan always go directly to the battery, the auxillary power is trigger by the ignition power, and the on/off pulse is triggers by the thermostat.

[Wulfgang]

Yeah, don't wire that sensor in series with the fan. It is not designed to pass that much current. It should be in series with the relay that controls the fan motor. Since your S13 should already have the sensor wired to the relay, and the stock electric fan wired to the relay, just use that circuit.

[Project240]

The stock fan was belt-driven...

[Nameless EJ6]

Use a relay whatever you do.

If I were you I'd run a relay powered by the fuel pump to activate it and keep it on (this isn't going to hurt fuel pump voltage don't worry), then run the power to the fan from the relay from an appropriate power source of your choice..

[BoostFab]

study this diagram,

scan through this page and get the idea, click here

[Wulfgang]

The stock fan was belt-driven...

Lol, not that one! There was also an electric stock fan.

[Project240]

OK, let me make sure I got this right. (I'm studying that diagram and that link, but it's throwing me off because the thermostat on this fan doesn't quite run that way...)

This fan control box has its own temperature sensor/thermostat coming straight off the box and running into the upper radiator outlet. It has one 12V wire for constant power (with a 20A fuse) running straight to the battery. It has another wire for ground, and the final wire (which I'm inquiring about) that should run to the ignition switched 12V power source.

So, what I should do is get a relay, run a wire to it from some ignition-activated wire (like the fuel pump wire), and have the 12V power run through the relay to the fan from some source (probably straight from the battery). Is that the basic idea? Just want to make sure I have this straight...

[Nameless EJ6]

Yes you're right.

Relay is powered by a 12v source to activate (close) another circuit for the fan. You can choose your own power source for the fans.. I've always been a bit skeptical about wiring them directly from the battery though.

[Project240]

Ok cool. Great advice guys. Thanks a lot for helping me to keep from frying my car that I've been waiting to drive for 2 years