cooling fan override switch

[vzimmer113]

I read fyrfytr1717's post about the radiator fan override switch found here... http://www.naxja.org/forum/showthread.php?t=1025399

It's a really good post and its very informative about how to hook up an override switch if you want to try to do it. I think I'm going to try to tackle it soon, using his post as a guide.

If you read the post, it tells you that the switch you mount in the cab is switching the ground, as opposed to switching the 12v power. So my question about this is if I plan on using a little LED rocker switch to go along with my fog and driving light switches, how to I wire them so that the LED indicator still comes on when the switch is turned on? The switches have 3 terminals on them, obviously one for a 12v power source, one for the accessory, and one for the ground. Is it as simple as I think by just switching the 12v power source to the ground on the switch and the ground to the 12v source? Or am I wrong...

[jeeperjohn]

You want to use a relay and switch the power source to the fan. Use the switch in the cabin to activate the relay.

[fyrfytr1717]

Originally Posted by jeeperjohn

You want to use a relay and switch the power source to the fan. Use the switch in the cabin to activate the relay.

Jeeperjohn, check out my write up. It takes a different approach than the usual relay switched secondary power wire running to the fan. It actually piggybacks onto the factory circuit and fools the fan relay into thinking it's getting an activation signal from the PCM. No need for additional power wires, fuses, etc.

Originally Posted by vzimmer113

The switches have 3 terminals on them, obviously one for a 12v power source, one for the accessory, and one for the ground. Is it as simple as I think by just switching the 12v power source to the ground on the switch and the ground to the 12v source? Or am I wrong...

Here's a summary of my reply to your PM:

That's essentially how I wired mine. Incoming 12V+ became an Incoming 12V-, Outgoing 12V+ to relay became an Outgoing 12V- to relay, Light Bulb Ground was hooked up to a constant 12V+ source. I'm pretty sure that's just a different way of saying what you said above.

Here's the catch though... LED's only pass current one direction. By hooking up the ground to a 12V+ and making the incoming 12V+ a 12V-, I think you are going to run the circuit the wrong direction. I'd try hooking it up on the bench top before you get too carried away with permanently wiring it.

The only way I could see it working is if you were able to pop open the switch housing, remove the LED, and solder it back in with the polarity reversed. I'd imagine that would be very difficulty to do without destroying the switch. You may end up having to get an incandescent lighted switch if you want the bulb to work.

[Lowerider33]

Can you wirexa switch to the aux fan without using a relay?