Indicator light for fan override switch

[zilverx]

Working on the dash wiring - not my favorite task. The dash is upholstered and populated with gauges, switches and lindicator lights, one being an indicator light to show when an override switch is used to to activate the engine cooling fan. My kit is from 2014 with the later wiring harness with 2 green wires for the fan ground. I used a sending unit on the intake manifold to control the fan used the other green wire for the manual switch. Now that I am committed (or should be) I want to have the indicator light come on when the dash switch is used. I thought about using a power source for the light and then grounding to the dash fan switch so it doesn't light until the switch is tripped. Would this work - ?

[brewha]

I could never get it to work properly. I could get the light or the fan to work I wouldn’t waste that light sensor on anything that useless though. I use the switch to cool the motor when I shut off the ignition which powers my Fitech. You will hear the fan running with the engine off. I use the extra light with this sensor and it has saved me twice already. https://www.ronfrancis.com/prodinfo.asp?number=LS%2D11

[skidd]

I don't know how the green wire is setup with your wiring harnesa, but I assume grounding it turns on the fan relay? If so Yes, it should work fine. Separate 12v to the light, and then grounded to the green wire side of the switxh. Closing/grounding the switch will complete both circuits. Triggering the relay, and light.

You could also use a DPDT switch. Use one side for the fan override, and the other side just for the indicator light. Simple, and little risk of the light affecting the fan relay or anything. Plus, you could easily disable the light if you find it annoying.

[CraigS]

I am not sure how the fan is powered in that harness. Will it operate w/ your toggle switch w/ the ignition off? If it will, I can see adding in a light in case you don't hear it as you leave the car. If it won't like my old MkII, I would skip a light.

[zilverx]

Thanks all for the input. As I understand, the dark green wires are grounding to a switch or sending unit and the circuit is not complete until the switch or sending unit closes. I may try build a model on the workbench to see what works (or doesn't).

[RBachman]

Why not install an illuminated switch?

[zilverx]

I like the idea of the double pole switch and just ordered a couple from Factory Five. I went with the DPST one, normally used as the Hazard switch.
Also, didn't consider an illuminated toggle as I wanted to keep it looking as closely as possible to the other toggle switches.

[Papa]

I would think this type of circuit would accomplish what the OP was asking about:

https://thefactoryfiveforum.com/attachment.php?attachmentid=124226&d=1584473457

This should allow the fan to be controlled automatically by a thermal control switch or EFI fan control or via an override toggle switch. When the switch is on, the lamp would be lit.

The two green Fan Thermo Control wires in the RF harness (one in the sending unit harness and a second in the front harness) both tie together and act as a ground trigger for the fan relay. If either green wire is grounded, that activates the fan relay which then provides power through a 30 Amp fuse to the blue fan wire in the front harness. The override switch is carrying no current and simply connects the green thermo control wire to ground manually. The mechanical thermal switch or negative control EFI fan control do exactly the same function. With the lamp wired on the (+) side to the fan power wire and the (-) side to the override switch (-) output, it will light when the fan is on and the override switch is on. If the override switch is off, the light will not come on when the fan is activated via the thermal switch or the ECU fan control as long as you use a double pole switch (4-pin) with one pole for the thermo control wire and one for the lamp (-) side.

[Derald Rice]

I just use a DPDT off-on-on toggle. In normal operation, as long as it is aligned with all of my other toggles, all is good.

[Papa]

I just use a DPDT off-on-on toggle. In normal operation, as long as it is aligned with all of my other toggles, all is good.

Either DPST or DPDT switch will work. If you want to match your other toggles, order another hazard flasher switch from FFR and use it the same way you are for the flashers with the feed on the two center pins and the outputs on the two pins on either end of the switch.

[Derald Rice]

Either DPST or DPDT switch will work. If you want to match your other toggles, order another hazard flasher switch from FFR and use it the same way you are for the flashers with the feed on the two center pins and the outputs on the two pins on either end of the switch.

DPDT allows for a manual over ride, and a quick visual of the toggle tells me what mode the fan is in.

[zilverx]

A Hazard switch is on the way from FFR -

[brewha]

Now that you don’t need the idiot light anymore, you can use it to monitor your charging system and battery health. You’ll be thankful you did.