Ignition Light/Charging Light

[barryhercules]

lo!, just been out for a lovely blast. Car running like a dream .... wait for it ..... charging light comes on, weird i thought, pulled over had a bit of prod round alternator everything looks ok. Decide to get back home in case she's not charging. Light goes out. Get back home check voltage and it looks like the alternator is not charging but the weird thing is the charging light is now not coming on at all, even when i pull the connections to the alternator? Anybody have any ideas?

Hope you managed to get out today!

[spend]

Bulb / Led gone? Light should come on when the ign is on & the engine not spinning (pulling the connector on the alt will turn it off..)

Dave

[barryhercules]

Ok could be a faulty bulb, the cars a serp so i thought they were leds? never heard of an led failing like that. Before i pop the dash top off should i not be expecting some voltage at the coil energising spade connector because there is nothing. The main alt feed has 12v so im guessing the 100a fuse remains intact.

[Cider Andy]

If it has the ignition and oil lights in the bottom of the speedo the charging light is a lamp, otherwise it's an LED.

The fact that the light came on whilst driving and now doesn't come on at all would make me think it's an alternator fault. Other possibilities are mutiple connector faults at the alternator, which is unlikely, or there's no earth to the engine which is also unlikely (starter motor wouldn't work).

[barryhercules]

ok that was fun, dash top now off nothing wrong with the bulb. Should i be expecting +12v at the bladed connector at the alternator or not?

thanks for your help guys.

[blitzracing]

Thats it, the bulb provides a 12volt supply that allows the alternator to start charging. If you ground this connector to chassis the dash light should come on as a simple test.

mark

[spend]

blitzracing said:

Thats it, the bulb provides a 12volt supply that allows the alternator to start charging. If you ground this connector to chassis the dash light should come on as a simple test.

mark

There should be a resistor in parallel with the bulb, so that in the case of bulb failure the alternator is still excited

You need the 12v at the small spade on the alt when starting it spinning, at which point it 'kick starts' the field coils (in lieu of big magnets ala dynamo). Thereafter @11.8v comes out of the alt on that spade, if your battery voltage is @14.v it can make a led glow - the subject of many perturbed owners

Dave

[barryhercules]

Ok im really stuck, theres nothing wrong with the bulb i dont get +12v at the bladed connector on the alternator no resistor visible on or around the buld connection... any clues guys or schematics?

cheers

[spend]

12v to the bulb is ignition switched, same one that powers all your dials.

Dave

[barryhercules]

Ok right off i go with the meter then! cheers.

[barryhercules]

Ahhhhh it seems that the bladed connector is not the one linked to the charging light after all. After a bit of wire tracing the other end of the bulb connector ends up on the alternator and if i ground it the light lights up! So does this mean the rectifier is knacked? next step is alt off but can i get new rectifier if needed?

as ever thanks!

[barryhercules]

Whoops, dont want to leave this open ended id forgotten about this thread..... So I got a new regulator and fitted it. Everything working hoon time, half an hour in lights start flickering get back home to find new regulator now popped.... So complete new alternator fitted and everything good.

Thanks for your help.