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Alternator tell-tail light conundrum
Posted: Mon Jun 12, 2023 10:28 pm
by hair bear
Here's a question for you...
If a 12v negative earth system is using the dash board tell-tail bulb for the exciter line, what would happen if I upgrade the bulb for an led equivalent to make it brighter, remembering the led will only allow current to travel one way.
All opinions, including sniggering, welcomed!
Re: Alternator tell-tail light conundrum
Posted: Tue Jun 13, 2023 9:19 am
by essexpete
Re: Alternator tell-tail light conundrum
Posted: Tue Jun 13, 2023 12:30 pm
by gecko.cx
The lamp only needs to pass current one way, so the fact it's a diode isn't the problem.
The problem is that it requires so little current to light an LED, it won't excite the alternator.
If you use 2W LED, it will excite the alternator and there is little chance you'll be able to ignore it.
Edit:
For reference, 2W is about right - (it's not just a random number)
Re: Alternator tell-tail light conundrum
Posted: Tue Jun 13, 2023 11:14 pm
by hair bear
Thanks for the insights, I think I'm leaning towards the 'leave well alone' verdict for the moment as this machine needs lots of other things done as well.
Cheers.
Re: Alternator tell-tail light conundrum
Posted: Wed Jun 14, 2023 7:43 pm
by essexpete
I have a similar issue with 2 agricultural trailers with led lights. There is not enough draw on the indicator circuits to light the trailer warning light on the tractor dash.
Re: Alternator tell-tail light conundrum
Posted: Wed Jun 14, 2023 9:43 pm
by hair bear
If the trailers are new they should have been fitted with resistors in the system to correct the draw. You get similar issues with can-bus cars and led trailers.
Re: Alternator tell-tail light conundrum
Posted: Thu Jun 15, 2023 4:24 pm
by essexpete
hair bear wrote:If the trailers are new they should have been fitted with resistors in the system to correct the draw. You get similar issues with can-bus cars and led trailers.
Not new but fitted from new.
Re: Alternator tell-tail light conundrum
Posted: Sat Jun 17, 2023 12:36 pm
by Slooby
essexpete wrote:I have a similar issue with 2 agricultural trailers with led lights. There is not enough draw on the indicator circuits to light the trailer warning light on the tractor dash.
You can get flasher relays designed to run LED's for just this situation
Re: Alternator tell-tail light conundrum
Posted: Fri Jun 23, 2023 12:38 pm
by essexpete
Slooby wrote:essexpete wrote:I have a similar issue with 2 agricultural trailers with led lights. There is not enough draw on the indicator circuits to light the trailer warning light on the tractor dash.
You can get flasher relays designed to run LED's for just this situation
How and where to fit?
Re: Alternator tell-tail light conundrum
Posted: Thu Jun 29, 2023 1:17 am
by Slooby
essexpete wrote:How and where to fit?
You replace the stock flasher relay with one like this:
https://www.ebay.co.uk/itm/272665874287 ... media=COPY