Full Version: Manual Fan Switch?
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Hi Folks,

After evicting the electrical gremlins with a new set of pulse generators, I'm adding a bit of insurance to the cooling system with a manual switch for the fan. It's a lighted toggle that I had on hand. It has three tabs: power, load, ground. I have also installed an LED lamp to tell me when the fan is running. I'm at a loss as to how to wire this up. The more I've read the more I've just confused myself... ...add in the fact that this is a bad back spasm day, I could use some help in some instructions on how to wire this up. Am I right in thinking that the manual switch completes a ground or do I have to supply it power? Do I get power from the thermoswitch or the fan connection? Time to go grab a cigar and stare at this some more. TIA.

Maybe this will help.

12 volts is applied to one side of the fan motor, then from the other side of the motor it goes to the thermo switch, when the switch closes (at the designated temperature) it then goes to ground thus completing the circuit and the fan comes on.

If you want to wire a switch in tap into the ground side of the fan and take that to your switch then to ground.
IF you want to wire in a LED tap the live side of the fan then to the LED from the LED tap the wire going from the ground side of the fan to the switch.

throw the switch, the fan should run also completing the circuit for the LED it should light.

..... er er I think Smile However on second thoughts the LED will not light if the fan comes on on its own this way. Another way would be to tap the positive side of the fan connect to a LED then to the ground side of the fan. THis way any time the thermo switch closed the LED will light. maybe two LEDs might be better one to come on when the switch is thrown (RED) and one to come on when the thermo switch closes.

This way you could have a LED showing the fan is running and one showing you have the switch thrown and the fan is running.

PS dont run the fan all the time A it isnt needed (better a warm engine than a cold engine) and you may drain the battery.
Tap into (without disconnecting) the wire between the fan and the heat sensing switch on the bike, this new wire goes to the manual switch power terminal, then the load terminal needs to go to ground. If you want the LED to light up then you will also connect that ground terminal to ground.

If in doubt about the switch use a voltmeter to check for continuity, and then a 12v power source to test the LED.
Thanks Tricky, UnionJack,

I'll give this a go tomorrow evening. The last of my Cubans are gone and the skeeters got pretty thick tonight. I mounted the switch and light on the handlebar cover. The switch is lighted, so that will tell me when the switch is on. I would like the LED to light when the fan runs with the thermoswitch. I'm gonna go over the schematic and see if I can't add some more confusion to the equation. I'll start running wires tomorrow. It might just be a process of trial and elimination. Thanks for the replies! It helps!
This should work

Power is applied to fan all the time
When thermo switch closes LED should light and fan runs
When you close the manual switch LED should light and fan runs

I think Smile

Because your not actually running large enough current after the fan I doubt there will be sufficient to light the manual switch
Great question and responses. I put in a manual fan switch last year and couldn't figure out how to get the light portion to light. When you solve it, I'll go back and add the wire to my switch.
i couldn't figure how to get the lighted switch on mine working since your are dealing with a ground circuit so i just installed an led up under the radio,worked better than the lighted switch because it was more in my line of switch
a blinking led would be an even better idea
OK, not as much time in the garage tonight as I would've liked. :cry: However, I poked and prodded and ran a couple test leads and this is what I've come up with:

[attachment=0] ^^^ THIS SCHEMATIC IS WRONG. DO NOT USE. (Scott.)

I want to cut the ground wire side of the thermstatic switch and wire the LED inline. Next, I want to use that ground and switch the fan on and off.
It works in my head. :-\
I have yet to implement this, but I think it will work. Tomorrow evening...... :YMSIGH:

I can't help you one bit, but if I was closer, I'd join you in the garage for a cigar!

cant see that working,the fanswitch still needs to be tied in the circuit as original,the ,manual switch is tapped into the ground circuit prior to the switch,the led is connected to the hot side of the fan circuit and the led is grounded when the switch is "on", exactly like tricky said earlier
There is no ground wire from the thermostatic switch, only from the manual switch.

You can add an LED between he manual switch and ground and it will light up when you turn on the fan manually, but the thermostatic switch is grounded by being bolted into the engine.
unionjack Wrote:There is no ground wire from the thermostatic switch, only from the manual switch.

You can add an LED between he manual switch and ground and it will light up when you turn on the fan manually, but the thermostatic switch is grounded by being bolted into the engine.

Nope the thermostatic switch is not grounded through the body.
Remember fellas,

I wanted the LED to light when the fan is operating with the thermostatic switch.

The switch I'm using is lighted. I want the light in the switch to come on when the switch is on and manually operating the fan. The manual switch is bridging the black wire and the green wire in my drawing. I think the LED will also light when this switch is thrown.

I also can confirm that the thermostatic switch does not ground to the switch body or thermostat housing. Hence, the need for a separate ground wire. The G (green) wire is ground. The Bl/Bu (black/blue) has power with the key on. The B (black) wire and the thermostatic switch complete the circuit for the fan.

It makes perfect sense rattling around in my skull. 8-X I just have to get the time to get out and do it.

Thanks for the feedback and support, guys. I be sure to let you know how it works out.
:!: :!: SUCCESS :!: :!:

I took the morning off to work on this. :d

This works exactly as pictured in my schematic above. ^^^
Interesting surprise too.
The LED only lights when the thermostatic switch is activated as the LED is directional.
:mrgreen: BONUS :d
I hadn't thought about that.

I will try to remember to grab a few pics before I button it up.
I'm doing the same thing but with an illuminated toggle switch. Going to tap into the power feed on the fan. Found two wires to the fan motor, a blue/black and a black. My meter is grounded to the battery and with the ignition on, neither wire has 12v power. Shouldn't there be power on one wire?
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