Alternator Repair: Faulty Field Winding?

Hello everyone,

'Since last week, my Passat 3B TDI (130,000 km) has been displaying 'Generator Workshop' on the FIS (multifunction display). An initial measurement showed that the alternator is no longer charging. I then replaced the voltage regulator with new brushes -> Result: still the same problem.'
Jetzt hab ich den neuen Regler wieder abgebaut und den Widerstand der Ankerwicklung über beide Pole des Ankers gemessen. Dieser geht gegen unendlich. Erwartet hätte ich einen Wert unter 100 Ohm. Ich würde sagen der Anker ist hinüber. Was Do you mean?
It's a Valeo Lima with 120 amps.

Best regards,
Stefan.

Hello.

Quote:

This one is going towards infinity. I would have expected a value below 100 ohms. I would say the inductor is broken. What do you think?

Definitely, I agree. The rotor winding is completely messed up. It's likely that we'll need to install a replacement alternator.
Best regards,

Quote:

Definitely, I see it the same way; the rotor winding is completely messed up.

It's likely that we'll need to install a replacement alternator. }
Normally, a DC voltage from the slip rings is applied to the armature. If you measure a resistance in the "infinite" range, then the armature winding is damaged; no excitation current can flow, and the alternator is dead...


Are there any visible signs of damage to the anchor externally? If so, is it possible to measure a short circuit against the shaft? However, even if that's not the case, the alternator is faulty.


Best regards, Holger.

Yes, definitely broken/damaged.
But you can have the anchor re-wrapped, or even just replace the anchor itself, especially if it's already being disassembled.
However, I can't say whether the price is really worth it.

You're talking about the claw-pole commutator here. It should have a resistance of approximately 3-5 ohms. If your multimeter (with the continuity tester) doesn't beep when you measure across the slip rings, then the winding is broken. I once had a situation where the ends of the winding were unsoldered from the slip rings.

"However, it's relatively easy to replace. A Bosch alternator costs around €100, and the Valeo will likely be similar. Before replacing it, you should measure the diodes and, of course, also check the stator winding (which is very rarely broken). If the diodes are also faulty, then it's better to replace the entire alternator."

I've experienced problems with defective Valeo rotors several times before.

The cause is a loose winding of the conductor coil, which leads to the connection wires to the slip ring vibrating loose.
I have had a lot of success by soldering new cables from the commutator to the break in the winding and securing everything with epoxy glue.

Unfortunately, it's very time-consuming (glueing - waiting - glueing - drying...), and I always do it in the evenings while watching TV.
made when my wife was working the late shift...

I don't have any pictures right now, but I will take some next time.
If someone is serious about preserving their rotor from being scrapped, they can contact me for more information.