Not Charging

[Bilkob]

Obviously it was all going too well.....
My GTI Turbo has stopped charging it's battery. Any quick checks/advice? Or is it simply get a new alternator....?

[white exec]

Alternator could be faulty (eg duff internal regulator pack), but before condemning it check this...

For the alternator to produce an output, it needs one (sometimes two) +12v inputs.
I don't have the CX circuitry, but connections to an alternator are typically:
- Ground (engine frame/chassis)
- Main output
- +12v batt (permanent live - may also be via a Fuse)
- +12v IGN (via IGN sw)
- and sometimes one more "voltage sensing" wire, going back to Batt+.

Check out the last three (or two), and any Alt Fuse on the car.

[Hell Razor5543]

I had a BX a long time back, and the alternator on that stopped charging. This was because the brushes had reached the end of their working life and worn out. I was able to get replacement brushes for around £12, and the alternator worked again. I got them from Thames Valley Electro Diesel in Reading (they are still trading).

[sparksie]

Alternator could be faulty (eg duff internal regulator pack), but before condemning it check this...

For the alternator to produce an output, it needs one (sometimes two) +12v inputs.
I don't have the CX circuitry, but connections to an alternator are typically:
- Ground (engine frame/chassis)
- Main output
- +12v batt (permanent live - may also be via a Fuse)
- +12v IGN (via IGN sw)
- and sometimes one more "voltage sensing" wire, going back to Batt+.

Check out the last three (or two), and any Alt Fuse on the car.

Okay, not quite, but for a novice, and assuming measurements are taken with the wires disconnected from the alt, it'll do.
Ground is usually, on cars anyway, through the frame.
B+ is usually direct to the battery, so will measure battery voltage, unless there's a problem in the connections, or cable.
D+ is the connection from the dash warning light. The current that lights the bulb also excites the alternator by magnetising the core. This one, as it provides the ground connection for a bulb, will only measure anything approaching battery voltage when the alternator is running AND charging.
However, when disconnected, with the ignition on, the cable should measure full battery voltage. If it does not then either the bulb, or the ignition switch, or perhaps the wiring between them, is at fault. Worth noting that, if the battery warning light bulb fails, the alternator usually won't charge.
W is a connection direct to the AC windings, upstream of the rectifier, used for pulsing a tacho, though I actually don't think Citroen use this method.
Finally, as you say, there is sometimes another, smaller B+. This is rarely found on cars. It's a feature of "Battery Sensed" alternators and is more commonly found in recreational vehicles, or boats, where there might be a splitter to separate the starter battery from the house battery. These drop the voltage slightly, so it's beneficial for the alternator to be able to measure the voltage at the battery post, rather than at the output stud on the alt. Most cars don't need this ability and so they're fitted with the cheaper "machine sensed" alternator.
All of that applies to conventional alternators, with a built in regulator.
Older, or newer types will be more complex. Older ones have an external regulator, while newer ones are controlled directly by the car's ECU.
Hope some of this is useful...

[white exec]

Good detail. I forgot to mention the need for a working dash indicator bulb.
If investigation fails, an exchange alternator is probably the next move. Beware cheap or unbranded ones though.

As a CX, the alternator and its wiring will be relatively straightforward. Maybe someone here can post a circuit diagram. Haynes should provide something reasonable, if stuck. Could you post your VIN, which will help?

[Bilkob]

New Alternator fitted. All sorted.Bingo

[white exec]

Bingo. How many years had the old one done?

[Bilkob]

Gawd knows.... Enough!