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[charlie]

on the alternator what does the thin wire do

[KillerWatt]

Provides current to the rotor (which turns it in to a magnet), which in turn induces a current in the output windings when it's spinning.

[charlie]

what kind of currant, volts, amps, how much should there be

[tunnie]

what kind of currant, volts, amps, how much should there be

14.4v  :-/ ish, i think!

[charlie]

if theres14.4 volts there, would there then be no need for an alternator :-/

[KillerWatt]

With ignition on and engine NOT running, you will see pretty much battery voltage.
With engine running, the voltage will depend on how hard the alternator is working (it sure as s**t won't be anywhere near 14.4v though).

[charlie]

so you put battery voltage in with the thin wire it makes the alternator magnetic and then the alternator produces electric 14.4or there abouts,thous making more than it uses.

[Andy H]

Provides current to the rotor (which turns it in to a magnet), which in turn induces a current in the output windings when it's spinning.

This wire goes to a lamp on the dashboard which switched on with the ignition circuit.

With a good alternator and a good battery very little current is required to energise the rotor and so the lamp doesn't light up (even though current is flowing through it). If the alternator cannot achieve 13.8v-14.4v then it draws more current to energise the rotor and the warning lamp lights up.

The alternator on an Omega is a bit more sophisticated than the above description because the thin wire is also used to operate a relay that prevents the rear screen heater working until the warning light goes out (at least it is on the Carlton/Omega A).

Edit - on the Omega B they seem to have used it to inhibit the operation of the self levelling suspension compressor.

[Andy B]

Why don'y you just take your alternator to a good local auto-spark and ask him to test it?      If the alternator passes you then just take the whole car back to him & get him to fix it ... that's what I did last with the Astra.       

[charlie]

i think its looking that way  andy

[Andy H]

With ignition on and engine NOT running, you will see pretty much battery voltage.
With engine running, the voltage will depend on how hard the alternator is working (it sure as s**t won't be anywhere near 14.4v though).

Not true

With the ignition on but the engine not running the battery symbol should illuminated on the dashboard. The voltage at the alternator should be near zero volts (otherwise the warning lamp wouldn't light)

With the engine running the voltage on the small wire should be very close to the alternator output. (ie 13.8v - 14.4v)

[KillerWatt]

With ignition on and engine NOT running, you will see pretty much battery voltage.
With engine running, the voltage will depend on how hard the alternator is working (it sure as s**t won't be anywhere near 14.4v though).

Not true

With the ignition on but the engine not running the battery symbol should illuminated on the dashboard. The voltage at the alternator should be near zero volts (otherwise the warning lamp wouldn't light)

I was talking with respect to the plug being disconnected.

[Andy H]

With ignition on and engine NOT running, you will see pretty much battery voltage.
With engine running, the voltage will depend on how hard the alternator is working (it sure as s**t won't be anywhere near 14.4v though).

Not true

With the ignition on but the engine not running the battery symbol should illuminated on the dashboard. The voltage at the alternator should be near zero volts (otherwise the warning lamp wouldn't light)

I was talking with respect to the plug being disconnected.

Plug?

The alternator connections on the Omega use threaded studs with a nut & washer to secure the cables.

Running alternators disconnected used to be a quick way of frying the alternator diodes, maybe they are more tolerant nowadays.

[Marks DTM Calib]

This little diagram shows quite nicely how it works.



So, the battery supplies the initial current to the field winding (via the brushes and slip rings) to energise the rotor. As a result the stator windings now start to ouput current thanks to the rotating magnetic field of the rotor.

This in turn is then rectified by a diode pack (3 phase) and 12+V is created....as both sides of the dash bulb now have 12Vish on them, the bulb extinguishes.

Now, the above is actualy how it was done some 20 years ago.....its a bit more sophisticated now but, it gives you the idea!

[KillerWatt]

Plug?

Plug, individual connections, whatever.

Running alternators disconnected used to be a quick way of frying the alternator diodes, maybe they are more tolerant nowadays.

I don't recall recommending that the alternator be disconnected with the engine running, if anything that is a very good way to lose digits at the very least.


As Mark says, his description of how it was done 20+ years ago is the "basics"......and I thought we were keeping the explanations basic because it is obvious the OP is struggling to come to terms with how it works.