Electric Fan

[bucketkids]

When you install a fan do you need to have it thermally regulated? How about if motor runs it runs? It's florida so you almost always need it anyway. I tried to take some recent build pics'. I finished the brakes, working on dash. Got electric water pump on. Thats when the fan thing dawned on me....

 

[ellis8500]

Your electric fan should be connected through a relay to a thermal on-off switch. The fan should come with connection instructions and some come with the relay and sensor kit.

 

[Lee_in_KC]

I originally had my fan wired through the ignition switch (with a relay) so if the key was on the fan was on. I was finding on all but the hottest days the motor was running too cool... seldom over 160*. So last year I put a thermal switch in the head (SBC) set for 210* on, 190* off and now the motor runs at a constant 200*, which from what I've read, is about ideal. You want the motor hot enough to evaporate the moisture in the oil.

You may already know this, but just to emphasize, regardless of how you trigger the fan, you really need to run a relay between the controlling switch and the fan. There are two reasons, the first being that those fans draw a lot of juice (mine is 30 amps), which is way more than most switches are designed to handle, and secondly, if you don't electrically isolate the fan from the ignition system, when you turn off the key the fan will continue to energize the circuit as it winds down. The inertia of the fan turns the fan motor into a generator as it spins down. This can cause "run-on" of the engine after the key is turned off.

 

[RPM]

I originally had my fan wired through the ignition switch (with a relay) so if the key was on the fan was on. I was finding on all but the hottest days the motor was running too cool... seldom over 160*. So last year I put a thermal switch in the head (SBC) set for 210* on, 190* off and now the motor runs at a constant 200*, which from what I've read, is about ideal. You want the motor hot enough to evaporate the moisture in the oil.

You may already know this, but just to emphasize, regardless of how you trigger the fan, you really need to run a relay between the controlling switch and the fan. There are two reasons, the first being that those fans draw a lot of juice (mine is 30 amps), which is way more than most switches are designed to handle, and secondly, if you don't electrically isolate the fan from the ignition system, when you turn off the key the fan will continue to energize the circuit as it winds down. The inertia of the fan turns the fan motor into a generator as it spins down. This can cause "run-on" of the engine after the key is turned off.

A simple solution to the run on problem. Run those items off the accessory side of the ignition switch. This includes the alternator.

 

[bucketkids]

Thanks everyone. Found everything in speedway to make temp controlled and on a relay. Sure am glad for the relay advise. Didn't even think a fan drew that much. Cheers!

 

[rooster57]

If you mount your relay low on the fan shroud and feed it from the alt. You can turn the relay on and off from the temp sensor on the block this equals no wireing in the car at all. This is a tip from your uncle Rooster

 

[rooster57]

This is where i made my relay mount and it kind is hidden by the shell. Its a circuit breaker and a relay. The last pic is my helper he keeps the neighbor from borrowing my tools.

 

[Rick]

Thanks everyone. Found everything in speedway to make temp controlled and on a relay. Sure am glad for the relay advise. Didn't even think a fan drew that much. Cheers!

I bought the American Auto Wire Harness and it has a built in relay and wires.Just screw in the sending unit and hook up 1 wire and bingo 180 and its on.

 

[bucketkids]

First, Rooster, I love the way you mounted the fan.

Now for the next question, Rick, I got a small Hay Wire kit that has nothing for fan, fuel Pump. My guage set came with a thermostat. Now here's the 100 dollar question. Does the same thermometer (sensor) go to the guage and the fan. through the little brain bos of course???

I'm moving forward,,,,, 1 wire at a time....

 

[bucketkids]

Oops, wrong pics.

 

[rooster57]

They do 2 separate jobs one is a n/o switch for the fan 180 or what ever it closes supplies a ground for your relay to turn the fan on . DONT try to run 12 volts to the fan sensor if its a one wire when it closes it will go to ground. And the other sensor for you gauge outputs metered voltage to the gauge as the temp rises for the lack of a better term. It will take two sensors. Sorry rick i just noticed this was directed at you.

 

[Rick]

First, Rooster, I love the way you mounted the fan.

Now for the next question, Rick, I got a small Hay Wire kit that has nothing for fan, fuel Pump. My guage set came with a thermostat. Now here's the 100 dollar question. Does the same thermometer (sensor) go to the guage and the fan. through the little brain bos of course???

I'm moving forward,,,,, 1 wire at a time....

You will have two wires comeing from the relay one hot and one ground.The hot wire goes to the fan and the ground goes to ground.The ground wire from the fan goes to the thermal sensor in the block.When the sensor reaches the set degree it grounds out and starts the fan when the engine cools enough it looses ground and the fan shuts down.Hope this helps.Rick
You migh have an internally grounded relay in which case no wire goes to ground but the rest is the same.

 

[rooster57]

I will just add something if the ground wire from the fan goes to the sensor it removes the reason for having a relay because the sensor will see all the current form the fan motor . I dont want to be arguminitive but this is a diagram i have drawn and will help you see what the reason is for having the relay . JMHO

 

[rooster57]

oops

 

[Rick]

oops

My drawing from American Auto Wire shows a fused 12 volt ignition sourse going to the relay pink wire(trigger).A 12 volt battery or ignition sourse fused red wire. Orange wire to fan(hot).Black wire to the fan temp switch (ground).I dont want to argue either But the pink wire is the trigger source.The red wire is the voltage to the relay.The orange is the voltage to the fan.The black wire is to the fan temp switch or you can use an on off switch which is the ground source.

 

[Rick]

My drawing from American Auto Wire shows a fused 12 volt ignition sourse going to the relay pink wire(trigger).A 12 volt battery or ignition sourse fused red wire. Orange wire to fan(hot).Black wire to the fan temp switch (ground).I dont want to argue either But the pink wire is the trigger source.The red wire is the voltage to the relay.The orange is the voltage to the fan.The black wire is to the fan temp switch or you can use an on off switch which is the ground source.

OOOPS my bad you have to ground the fan then the fan temp switch grounds the relay.Sorry Rooster.

 

[rooster57]

Sorry isnt necessery i like a good discussion that gets us all thinkin.