Board logo

Charge light query
steve m - 10/12/09 at 08:13 PM

with a dashboard charge light, should it be wired from the alternator and from the and the plus side of the battery ?

ive rewired my car, and seemed to of cocked up the charging light ??

regards

steve

02GF74 - 10/12/09 at 08:25 PM

that is correct.

one side of lamp goes to switched 12 V and other to alternator.

note that this is not the main alternator output but the charge lamp terminal. (for wnt of a better description).

if your lamp is a LED, then it can only be wired one way; for a filamnet bulb it does not matter.

blakep82 - 10/12/09 at 08:47 PM

will an LED lamp have any problems lighting up properly. what with the alternator 'exciting' itself etc, will there be any issue with the tiny amount of current needed?

reason why i ask is because i got a starter button with led light, i want this to light up when the engine's not running, and go off when it is (like the battery light)
i also want a battery light too, so will both wired in be a problem?

sorry to hijack

steve m - 10/12/09 at 08:57 PM

Thanks guys, i thought i was right but it didnt work, so will look at tomorrow

regards

steve

britishtrident - 10/12/09 at 09:23 PM

Wire the LED up via the oil pressure switch.[


quote]Originally posted by blakep82
will an LED lamp have any problems lighting up properly. what with the alternator 'exciting' itself etc, will there be any issue with the tiny amount of current needed?

reason why i ask is because i got a starter button with led light, i want this to light up when the engine's not running, and go off when it is (like the battery light)
i also want a battery light too, so will both wired in be a problem?

sorry to hijack

blakep82 - 10/12/09 at 09:29 PM

^ ah, good call! hadn't thought of that
cheers

daviep - 11/12/09 at 08:58 AM

An LED may not pull enough current to excite the alternator.

Land Locked - 13/12/09 at 07:32 PM

quote:
Originally posted by daviep
An LED may not pull enough current to excite the alternator.

LED on it's own will not pull enough current.

This layout will. It's a modified copy of a diagram that someone on the South African Locost forum found. I did the mods based on my own experience with some stationary engine controllers.

The 100 Ohm resistor at 2 W gets VERY hot. 5W is a minimum. The 1n4007 can be any 1 amp diode, it stops back feed.



[Edited on 13/12/09 by Land Locked]

MikeRJ - 13/12/09 at 08:18 PM

Not convinced the diode is really needed in the above; there should be no back feeding from the alternator. If there were then it would cause problems with a conventional filament lamp as well.