Hi All,

I have fitted an LED charge warning light but it will not go out and the alternator will not charge, but if I change the LED for a standard bulb all is fine.

Link to the warning light I'm using

Can anyone explain why the LED doesn’t work and is there a way that I can still use my LED warning light.

The alternator is a Lucas with this terminal layout:-


Lucus alternator terminals

The two large terminals are going to the positive on the battery and the small on is connected to the warning light via a switched live.

Yours hopefully

Rob

[Edited on 15/10/2007 by RobH]

The alternator requires a certain amount of current through the charge light to function correctly - it's part of the way it works.

If you really want a LED you could either wire a bulb in parallel and hide it somewhere, or use a wire-wound resistor of a suitable value (but it might get hot occasionally - but only when lit! ).

David

[Edited on 15/10/07 by David Jenkins]

I put a resistor in parallel with the LED and it's drop resistor. I used a 72 ohm resistor, and figured it needed to be a minimum of 2w for safety. Works a treat.

Cheers
Richard

Thanks for the reply David.

I really want to use the LED because it matches the rest of the dash.

Do you have any idea what value resistor I might need.

Rob

Thanks Richard

Your answered my question while I was typing (very slowly)

Rob

[Edited on 15/10/2007 by RobH]

Yeah you need the current through the bulb to excite the field windings. Oh errr missus....

Doesn't need to be much. 72 ohms should be OK

Thanks for all the replies Guys.

I think you have all sorted it for me.

Thank you.

Rob

quote:

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I used a 72 ohm resistor, and figured it needed to be a minimum of 2w for safety.

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That will be 75 Ohm then, as they don't produce a 72 Ohm resistor.

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SixedUp - 16/10/07 at 11:33 PM

Could be ... 72 ohm was what I worked out I needed, I'd have bought whatever was closest when I was next passing Maplins :-)

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VinceGledhill - 17/10/07 at 10:18 AM

See avatar ;-)

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