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MG MGA - Warning light on fan override switch

What I thought would be a simple wiring exercise is turning into a mystery saga. I have a Revotec fan wired with an override switch. The switch is a normal on/off toggle..current to Off, and earth to On. I want to wire up a visual warning light in conjunction with the toggle switch operation, just as a reminder that the fan is on override. The light is an LED one, and I cannot fathom out a wiring schematic for it to work..Revotec tell me that I will need a different switch containing a diode. Any ideas anyone? BTW, I'm operating on negative earth.
Gary Lock

Hi Garry
So you're saying you have to put the fan operating wire to earth through the switch to make the fan operate---?
Where is the 'current to Off' coming from
William Revit

If I remember correctly the switch earths the relay to operate the fan, so either:

1. take an ignition switched feed to the LED via a diode to stop the earthing of the relay while the switch is off and connect the other side of the LED to the "live" side of the switch, or

2. run a wire from the switched side of the relay to the LED and earth the other side of the LED - this will also light the LED whenever the fan runs, so is an indication it is working.

Chris at Octarine Services

Yep as Chris describes, I just found a wiring diag for your fan---

https://www.revotec.com/acatalog/070075.pdf

So as Chris says - 12v ign fed wire through your LED globe to the same terminal on your toggle as the blue wire in the diagram

Gosh you're quick Chris I went to find the diag. and you were here already
William Revit

I take it that you have 2 wiring terminals on your Led or is it one of those earthed bases with one post
William Revit

I had never even thought of fitting a warning light to my electric fans Gary and your post has made me wonder why that is.
Thinking about it, I have been running with twin electric fans on my radiator (and no engine driven fan) for quite a few years now, and when they switch on, I can definitely hear them run.

So maybe when my "earsight" :^) fails a little more, I will have to think about fitting a warning light.

Cheers
Colyn

PS Don't forget that LEDs are often very polarity-sensitive and if you connect them incorrectly, they often don't survive.
Colyn Firth

This thread was discussed on 10/12/2019

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