Alternator Light Can you Use an LED, Replacing the alternator light with an LED bulb Options

[LotusJoe]

Can you replace the alternator bulb in the dash with an LED? Will the circuit still operate correctly? (IMG:style_emoticons/default/confused24.gif)

[timothy_nd28]

No, the LED will cause your car to stop charging.

[LotusJoe]

No, the LED will cause your car to stop charging.

Thanks for the reply. Can I put a resistor inline; similar to one used in running light applications?

[timothy_nd28]

Yes you could add a resistor to simulate the same load, but then again why? I understand adding LED lamps to better help illuminate the backlighting, but there is no issue with the incandescent bulbs for the indicator ports. These port tubes direct the light to the filter lens, and is bright enough. I just don't understand what is gained from using LED's for indicators (IMG:style_emoticons/default/confused24.gif)

[Mikey914]

I just use a reg bulb for the charging circut. Also, An LED on the Oil light can illuminate at a lower voltage so it will be more sensitive.

[Mikey914]

Correct me if I'm wrong, but as I understand the circuit that activates the field is on the light, so the diode basically kills the ability to activate the field.

[nathansnathan]

The problem, as I understand it, is that the indicator light is in the middle of the charge circuit. Since an LED acts as a diode, only 1 side of it would be hot when it is on (neither side is hot when it's off), where a normal bulb the current flows 'through', showing current on both sides. Your battery won't be charging with an LED in there, resistor or not.

[LotusJoe]

Yes you could add a resistor to simulate the same load, but then again why? I understand adding LED lamps to better help illuminate the backlighting, but there is no issue with the incandescent bulbs for the indicator ports. These port tubes direct the light to the filter lens, and is bright enough. I just don't understand what is gained from using LED's for indicators (IMG:style_emoticons/default/confused24.gif)

The application is not for the 914. I also have a Lotus Europa which I put in a new wiring harness. When I rebuilt the dash I replaced all the indicator bulbs with LEDs. I realized the other night that the LED for the alternator by itself would not work. At this point I don't want to abandon the the use of LEDs so I'm trying to figure out a work around. I wanted to confirm that the LED would keep the charging system from working, but also I'm thinking a resistor should resolve the issue as well, the way it help create a load for the blinker relay when someone makes the conversion to LED running lights. So am I on the right track? Some of the other post would indicate otherwise. (IMG:style_emoticons/default/confused24.gif)

[timothy_nd28]

quick and easy fix "I think", keep the LED installed, but wire the incandescent lamp in parallel. Use some heat shrink around the bulb to kill the light.

[LotusJoe]

quick and easy fix "I think", keep the LED installed, but wire the incandescent lamp in parallel. Use some heat shrink around the bulb to kill the light.

I was thinking about doing that very thing. It would be a quick and easy solution.

[stugray]

The problem, as I understand it, is that the indicator light is in the middle of the charge circuit. Since an LED acts as a diode, only 1 side of it would be hot when it is on (neither side is hot when it's off), where a normal bulb the current flows 'through', showing current on both sides. Your battery won't be charging with an LED in there, resistor or not.

Actually that is close. The LED only flows a few milliamps of current to illuminate and that is all.
That is not enough current to "excite" the alternator winding to kickstart it.
Putting a high power 70 Ohm resistor in parallel with the LED works fine.

And the reason I replaced mine was that I pulled everything out of the dash and dont have the combo gauge. Matching FLAPS LEDs for the oil & Alt just made more sense.

[LotusJoe]

Actually that is close. The LED only flows a few milliamps of current to illuminate and that is all.
That is not enough current to "excite" the alternator winding to kick start it.
Putting a high power 70 Ohm resistor in parallel with the LED works fine.

And the reason I replaced mine was that I pulled everything out of the dash and don't have the combo gauge. Matching FLAPS LEDs for the oil & Alt just made more sense.

That is what I was just reading about. When wired in parallel does the resistor act like an incandescent bulb? What is the wattage of the factory incandescent bulb? A 70 Ohm resistor is about the equivalent of a 2 watt bulb. My old dash bulb was 2.5 watts. Obviously this works if you have already done the conversion.

[stugray]

When wired in parallel does the resistor act like an incandescent bulb?

yes, as a matter of fact you can just use the bulb if you want.

A 70 Ohm resistor is about the equivalent of a 2 watt bulb.

I started with the bulb wattage to come up with 70 Ohms.
Pwr = 2.5W = Volts*Current = V^2/R
using V = ~13.5 yields:
R = 72.9 Ohms

So the alt is expecting about .185 Amps.
I had some 140 Ohm, 1 watt resistors. I just put two in parallel and put that across the LED.

[LotusJoe]

When wired in parallel does the resistor act like an incandescent bulb?

yes, as a matter of fact you can just use the bulb if you want.

A 70 Ohm resistor is about the equivalent of a 2 watt bulb.

I started with the bulb wattage to come up with 70 Ohms.
Pwr = 2.5W = Volts*Current = V^2/R
using V = ~13.5 yields:
R = 72.9 Ohms

So the alt is expecting about .185 Amps.
I had some 140 Ohm, 1 watt resistors. I just put two in parallel and put that across the LED.

Thanks so much for your help. That's what I'll do. (IMG:style_emoticons/default/smilie_pokal.gif)