automotive electrical question


Old 12-23-10, 08:04 AM
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Join Date: Dec 2010
Location: america
Posts: 2
automotive electrical question

I am running electrical engine cooling fans on my 2000 f150.I installed a light in the dash connected to the fan power switch so that I would know when it is working.The problem is driving down the road the air moving thru the fan blades makes it spin which in turn generates power and turns the light on.I has an electronic controller with a relay that controls it in a 12v system. I was thinking a one way diode could take care of this. But I cant find anyone that can help me out
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Old 12-23-10, 08:41 AM
Join Date: Dec 2004
Location: Canada
Posts: 160
You could just hook your light up in parallel with the coil of the relay. This would let you know if the coil is energized and powering the fans. No diode needed.
The only possible downside to this is if the relay fails you will still get an indication on your light.

If you prefer to use the diode so you know for sure power is reaching the fan you can add one to the circuit between the output of the relay and the fan. Make sure the light is connected between the output of the relay and the diode and it will work just fine. The diode needs to be large enough to handle the current and if it fails you will no power to the fan.

Last edited by Buzz; 12-23-10 at 08:52 AM. Reason: To add a little more info
Old 12-23-10, 03:12 PM
Justin Smith's Avatar
Join Date: Dec 2010
Location: Cressona, Pa, USA
Posts: 2,546
Wire it like this:


Periods mean nothing.

Last edited by Justin Smith; 12-23-10 at 03:15 PM. Reason: displayed wrong

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