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Flo

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Member #: 6322
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Bawdeswell, Norfolk

20th Jan, 2012 at 12:23:40pm

Morning all.

When I fitted dash lamp for my alternator I tried to kill 2 birds with one stone, fitting an LED lamp (to match my illuminated toggles) instead of a Diode and a bulb. In honesty I didn't really need to fit a lamp as my Motogadget dial shows voltage (which is a healthy 14ish volts while the engine is running) but had already cut the hole in the dash. Unfortunately the resistance of the LED must be a whole lot less than a bulb, and instead of the LED going out while the engine is running, its brightness drops about half.

My question is about the best way to solve this? Change the LED to a bulb (although there isn't one to match the style, so would have to be modded by me...) or to fit an inline resistor? If I fit a resistor, what resistance would I require?

Thanks

Matthew

Carlzilla

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Quarry Bonk

20th Jan, 2012 at 12:28:51pm

I'm not sure if you're familiar of how the charging light works, it has to be a bulb so that the current can flow both ways through it. If the alternator is fine, the current at both ends of the bulb are equal, and so doesn't light up, if the alternator gives in, the current flows battery to alternator and the charging light illuminates telling you there is a fault, and vice versa. Hope that helps somewhat :)

Edited by Carlzilla on 20th Jan, 2012.

On 26th Jan, 2012 Tom Fenton said:
ring problems are down to wear or abuse but although annoying it isn't a show stopper

On 5th Aug, 2014 madmk1 said:
Shit the bed! I had snapped the end of my shaft off!!

17.213 @ 71mph, 64bhp n/a (Old Engine)

Flo

78 Posts
Member #: 6322
Advanced Member

Bawdeswell, Norfolk

20th Jan, 2012 at 12:37:08pm

Clearly I dont then! I just went by the MPI loom wiring diagram in the Haynes manual (my loom is a modified MPI loom) and (I haven't got it infron of me) I was sure it showed an diode inline before the bulb...

Carlzilla

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Quarry Bonk

20th Jan, 2012 at 12:51:11pm

Bear with me and ill have a look in my haynes!

On 26th Jan, 2012 Tom Fenton said:
ring problems are down to wear or abuse but although annoying it isn't a show stopper

On 5th Aug, 2014 madmk1 said:
Shit the bed! I had snapped the end of my shaft off!!

17.213 @ 71mph, 64bhp n/a (Old Engine)

Carlzilla

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Quarry Bonk

20th Jan, 2012 at 12:57:47pm

On the wiring diagram for my car, (89) you should have brown/yellow from the alternators charging pin, and then white from the ignition feed, one at each end of the bulb.

On 26th Jan, 2012 Tom Fenton said:
ring problems are down to wear or abuse but although annoying it isn't a show stopper

On 5th Aug, 2014 madmk1 said:
Shit the bed! I had snapped the end of my shaft off!!

17.213 @ 71mph, 64bhp n/a (Old Engine)

shellspeed

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Surrey

20th Jan, 2012 at 01:08:02pm

That explains why mine does not work properly as I earthed the otherside to the brown/yellow on the bulb. Spot of wiring this afternoon then. Cheers

apbellamy

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King Gaycharger, butt plug dealer, Sheldon Cooper and a BAC but generally a niceish fella if you dont mind a northerner

Rotherham, South Yorkshire

20th Jan, 2012 at 01:09:19pm

the white powers the alternator. you should also have white to the clocks to provide the other side of the circuit

On 11th Feb, 2015 robert said:
i tried putting soap on it , and heating it to brown , then slathered my new lube on it

*hehe!*

shellspeed

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Surrey

20th Jan, 2012 at 01:29:09pm

its been baffeling me since i made the wiring loom last year RTFM
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