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LED for Fan/Alt light
Posted by: jetcat ()
Date: July 08, 2019 10:36AM

Finished my conversion to modern gauges in my Corsa dash and one of the modifications required moving the warning lights to a new location. Super duper bright LEDs I felt was the best solution but unlike the oil/temp light, the Alt/Fan light does not get a full 12v to the bulb. To get full voltage, I made a simple circuit using a comparator IC to drive the LED to full voltage. If anyone else just wants to replace the standard bulb with a real bright LED, I'd be happy to post the schematic. It only requires putting the circuit in series with the existing bulb wires and attaching a ground wire to one of the screws holding the speedometer.

Bob
Paso Robles, CA

Central Coast Corsa
1966 Turbo Corsa convertible
1966 Corsa 140 coupe but now with 110hp heads.

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Re: LED for Fan/Alt light
Posted by: 66vairman ()
Date: July 08, 2019 01:16PM

jetcat Wrote:
-------------------------------------------------------
> Finished my conversion to modern gauges in my Corsa dash and one of the modifications required moving the warning lights to a new location. Super duper bright LEDs I felt was the best solution but unlike the oil/temp light, the Alt/Fan light does not get a full 12v to the bulb. To get full voltage, I made a simple circuit using a comparator IC to drive the LED to full voltage. If anyone else just wants to replace the standard bulb with a real bright LED, I'd be happy to post the schematic. It only requires putting the circuit in series with the existing bulb wires and attaching a ground wire to one of the screws holding the speedometer.

Correct, even when you reverse the warning socket wires for the correct polarity (for bayonet socket LEDs) the voltage is not great enough to power the LED for adequate illumination (some of the LEDs that are not polarity sensitive won't even turn on). This is true of the external regulated OR internally regulated alternators.

While your circuit is a nice fix, I went with a simpler fix -- brighter 1816 bulb in the standard Corsa gauge. With aftermarket gauges a LED warning lamp is nice.



Edited 1 time(s). Last edit at 07/08/2019 01:23PM by 66vairman.

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Re: LED for Fan/Alt light
Posted by: Spectre ()
Date: July 08, 2019 01:22PM

Those gauges look good in there.

David Clamp


1965 Corsa convertible - 140 4spd/3.55/AM-FM

2013 Mustang GT convertible - 5.0, 6spd auto, Procharger i-1

2003 Miata SE - 6spd manual (wife's toy)

"Victory is mine!" - SG

Norman, OK

<a href="[www.wunderground.com] src="[weathersticker.wunderground.com]; alt="Click for Norman, Oklahoma Forecast" height="90" width="160"></a>

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Re: LED for Fan/Alt light
Posted by: joelsplace ()
Date: July 10, 2019 09:05AM

Post it!

Joel
Northlake, TX
5 Ultravans, Lost count at 100 Corvairs...

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Re: LED for Fan/Alt light
Posted by: jetcat ()
Date: July 10, 2019 09:44AM

Sorry for the hand-drawn circuit. Hope you can read my printing.

Alt_Fan LED Diagram

My bulb (BRN to B/P wire) measured 6V when the engine was off, <1V when running and 12V when starting (key in start position - **only time the stock bulb was bright**). I adjusted the trim pot for a switch point around 8V but anything from 7V - 9V would probably work fine. If you don't have a trim pot then a resistor divider using a 2.4k to +12v and 7.5k to ground should be fine.

Keep the layout of parts close to the LM311N. They have a reputation to oscillate if you have long leads for the inputs. I put a large capacitor across the inputs to mitigate that problem. Checked it with my oscilloscope and it seems stable enough. The circuit, in theory, will drive up to 50MA @ 50V but I'd keep it under 25MA. That will drive 99.99% of the 12V super bright LEDs available.

The LM311N is available from Amazon, Digikey, Jameco or ???. About $6 for 15 of them.

Bob
Paso Robles, CA

Central Coast Corsa
1966 Turbo Corsa convertible
1966 Corsa 140 coupe but now with 110hp heads.

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Re: LED for Fan/Alt light
Posted by: American Mel ()
Date: July 10, 2019 10:17AM

WoW!
Those are BRIGHT !
If a person can't see those, they should not be driving.

-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
WA. state, 1 mile south of the Canadian border,
I am not at the end of the world, but you can see it from here.
Have; '66 Monza Coupe - 140, 4-spd. Daily driver beater
'67 Monza Vert. - 140, 4-spd. Daily driver beater
'67 A/C Moredoor Monza - Sale pending
Have had; '61 Monza coupe, '62 Monza Wagon, '63 Spyder, '65 Corsa
.
non-vair
'04 Dodge Cummins Quad Dualy, approaching 400K
17'Terry

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Re: LED for Fan/Alt light
Posted by: cnicol ()
Date: July 10, 2019 10:27AM

Your circuit relies on the factory 10-ohm parallel resistor to provide excitation current to the alternator?

Craig N. Coeur d'Alene ID.
66 Black Monza 4dr, 4.2L V8 49k
61 Seamist Jade Rampside 140 PG
60 Monza coupe (sold, sniff sniff)
66 Sprint Corsa convt - First car! Re-purchased 43 years later
2+2 gnatsuM 5691

+17 Tons of parts

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Re: LED for Fan/Alt light
Posted by: jetcat ()
Date: July 10, 2019 11:00AM

Yes, for an LM dash harness with an alternator. Relies on the 24 BRN resistor wire from the ignition switch to the main harness 12-pin connector.

You could add a resistor across the input of this circuit but it would not have the ignition switch "start" cutout. Not sure how much load you would need for the excitation. Some alternators will self excite when the RPM's are just above idle.

If I had an early, I would just use the 1816 bulb.

Bob
Paso Robles, CA

Central Coast Corsa
1966 Turbo Corsa convertible
1966 Corsa 140 coupe but now with 110hp heads.

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Re: LED for Fan/Alt light
Posted by: joelsplace ()
Date: July 10, 2019 12:33PM

Here it is in the forum instead of a DropBox account.
Thanks Bob!

Joel
Northlake, TX
5 Ultravans, Lost count at 100 Corvairs...




Edited 1 time(s). Last edit at 07/10/2019 12:34PM by joelsplace.

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Re: LED for Fan/Alt light
Posted by: jetcat ()
Date: July 12, 2019 07:22AM

I made another circuit with fixed resistors for my convertible. I took pictures of the layout if it helps anyone....

Bob
Paso Robles, CA

Central Coast Corsa
1966 Turbo Corsa convertible
1966 Corsa 140 coupe but now with 110hp heads.

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