Thread: electric fans on my radiator.- do they need to be thermostaticly controled??

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Can they just come on when I start the engine, and go off when I shut it off?

Nice and simple?

Thanks Jim

You can does this but it is not ideal. It can take too long to get to operating temp. Before I did this I would use a toggle switch to trigger your fan relay(you are using a relay right?)-Assuming that you have a working temp gauge.

Originally Posted by lucforce

You can does this but it is not ideal. It can take too long to get to operating temp. Before I did this I would use a toggle switch to trigger your fan relay(you are using a relay right?)-Assuming that you have a working temp gauge.

I went straight from the back of the fuse panel (an a leg that is switched with the key and supplyed with 12g wire) with 12g wire to the fans. 20 amp fuse. No relay. Why?

Thanks for the help BTW. Jim

The fan uses a lot of current. Wouldn't you use a relay to turn on the fan? If you don't use a relay, you will probably burn out your ignition switch.

If you will be using a relay anyway, it's really simple to use a temperature switch to control the relay, and this will extend the life of your fan motor, since it won't be running all the time.

To keep it real simple, I guess you could put a heavy duty switch on your dashboard, but you'd have to watch your temperature gauge carefully!! Be sure your relay or your switch is rated for at least twice the number of amps that your fan uses. Don't use a horn relay for your fan motor. Horn relays aren't designed for continuous operation. Be sure to use a fuse in your fan motor circuit.

What I do is run a temp switch on the motor to close the circuit on the relay and have an override toggle switch under the dash for when I get panicky. When running A/C the clutch circuit gets tied in here also.

Relay $5-$10
Temp Switch $5-$35 depending

I have the temp switch, it is threaded into the water jacket on the intake, with 2 small wires comming out, correct?

This switch is normally open?
I can control the relay with it?
How many amp relay?
I am using 2 fans, can I control them with the same relay and run one hot wire (12g) ? or do I need 2 relays and hot wires to the fans seperatly?

Sorry for so many questions, but I do apreciate the help.

I thought about the toggle on the dash, but decided against it, Hot Rod Roy, I quit flying my ultralite airplane for the same reason, likely pilot error !!!

thanks Jim

I do not know which switch you have.
Yes you can use it to trigger the relay with the proper wiring. Depending on the vehicle and the switch in question, you gan you the switch to supply the ground or the pos 12V to close the relay circuit.
use one 30 amp relay for EACH fan.

I used the Painless kit to do mine. Comes with the thermostat for the motor, relay, wiring and fuse or breaker. Kit was about $65 for all of it and made it really simple. You can add a switch to it if you want also.

Originally Posted by Beerstudd

I used the Painless kit to do mine. Comes with the thermostat for the motor, relay, wiring and fuse or breaker. Kit was about $65 for all of it and made it really simple. You can add a switch to it if you want also.

I too am running the Painless kit - but what I wanted to add is that they do have several temp senders from 165 to 210. There are also several others that have an adjustable rheostat that also works well, but have a long Bourdon tube that has to be contended with. Regardless of whatever way you go, you should still have a relay to kick it on as a fan draws a lot of start up current and can cause damage to other components.

My fan operates off a relay controlled by a 180 Deg. temperature switch. I also installed a toggle switch that will bypass the temperature switch in case of a temperature switch failure.

1 speed fans?

Single speed? Dont know. (maybe that is what the little black box does)

here is what I do know. Maybe you guys can help me identify it.
The relay is pluged into a little black box, with several wires comming out of it. It (the relay) was jumpered and cant trust how it was wired in, made no sense to me.
The little black box had some electronics in it with a pot showing( could be adjusted with a small screwdriver). 2 very thin wires came from the thermostat in the manifold to this little black box along with a couple hot wires (best I could tell) and a couple more comming out.
Does any of this make any sense to any of you?

Today I ran both fans into 10g wire all the way to the fuse box area. I am prepaired to make all the connections in that location. I tested the fans and they pulled 11 amps when running full speed and 21 amps starting up.

30 amp relay should do it? That is if I cant figure out how to use the existing relay, and that little black box.

What do you guys advise? (dont say sell the truck)

Thanks Jim

and your right Shawnlee, much longer and a bit more.

Hot switched wire to relay, relay to fan and 12v source. Bourdon tube to radiator and fan controller, to relay. Twenty bucks for the adjustable fan controller and sensor. A few more bucks for the relay and wire.

Balance that against when you will forget to turn it on or off with a manual switch and either smoke the charging system or blow out the cooling system and maybe lose the engine.

Originally Posted by w2zero

Hot switched wire to relay, relay to fan and 12v source. Bourdon tube to radiator and fan controller, to relay. Twenty bucks for the adjustable fan controller and sensor. A few more bucks for the relay and wire.

Balance that against when you will forget to turn it on or off with a manual switch and either smoke the charging system or blow out the cooling system and maybe lose the engine.

Your right. Not going with manual switch. I know how that would go, you nailed it.

One of those embarrassing memories I have of puking coolant all over the shop on the first startup before adding all those goodies.