23 replies to this topic

[Ethel]

The question is how is the battery energising the alternator windings without lighting the warning lamp? Could be a bit of a short, worth looking at the bulb holder if it has a centre speedo.

[jonb_5]

So basically there should be 12volts to the bulb when the ignition is on whatever is happening, if there isnt there must be a wiring fault somewhere??

Cheers

Jon

[lrostoke]

A quick test of the ignition circuit would be to set up a a bulb in a holder...run a 12 volt feed to it . the other connection connect to the ignition wire on the alternator (the thin one), you would need to cut the wire to get a decent test, but can be rejoined.

If bulb comes on with out engine running and goes out when engine started, then you've narrowed the problem down to the wiring going to the ignition light.

If bulb does exactly the same as the ignition light is doing, then I'd still suspect dodgy alternator or the main connection from alternator to solenoid.

The wiring to the alternator is really simple

ignition on sends a 12volt live to the ignition bulb, the other wire to the bulb goes to alternator (thin wire)

The only other connection to the alternator is the thicker wires which go to the solenoid and from there to the battery.

Edited by lrostoke, 06 December 2008 - 03:36 PM.

[jonb_5]

Hi,

Have just checked voltage with engine on and off, and reving slightly, all stay at around 12.7 volts.

I took the brown/yellow wire and grounded it and nothing happend.

I used a resistance buzz test and it worked fine, showing there is not a break in the wire.

I also used a multimeter on the bulb, the interesting thing here is that it only produced a voltage when i reved the engine, more voltage as the revs got higher, i am really stuffed on this one.

Can you help??

Cheers

Jon

[jonb_5]

I have just read your text over - did you say the bulb holder should have an ignition live and the earth going to the alternator.

Because if that is what you said i think this is our problem, as it is at the moment, the bulb holder as a earth, connected to the car chasis and the brown/yellow wire, connected to the alternator (this was an assumtion on my behalf)

I think this could be the problem???

Feel free to call me a numpty!!!

Cheers

Jon

[Ethel]

There should be 12v from the ignition switch going to the bulb, then on to the alternator where it completes the circuit through the windings. Once the alternator generates leccy, it will also produce 12v or more so the voltage on both sides of the bulb will near enough cancel each other out and the bulb will no longer light. If there's a bit of a short between the iggy switch and the bulb it could reduce the current going through the bulb enough to stop it lighting, once the alternator kicks in the short would be down stream of the bulb for volts coming from the alternator so it would light. I'm not saying this is the only possibility. As I said earlier, if you have centre instruments it's not unheard of shorts to develop with the instrument housing as that's how some other bulbs on the dash work.

[lrostoke]

OK your a numpty lol

Ignition light needs a 12v ignition switched live feed, the other connection on that bulb normally an earth goes to the thin wire on the alternator

[jonb_5]

I have rewired the bulb holder with a 12v ignition live from the voltage stabilizer and also the wire to the alternator - guess what,


IT WORKS!!

Thanks for all the help

Cheers

Jon

[lrostoke]

Not sure if it makes any difference, but the live feed should go from the non stabilized side of the voltage stabilizer (the white wire)