Hi, have been trying to fix an intermittent alternator fault in a Mexican Beetle for a while now. The car had a non-Bosch reconditioned alternator that is very commonly available. It is the type that has a plate on top held with 3 small screws. This removable plate has brushes underneath and also the rectifier so in some ways is considered to be an improvement. I replaced the alternator with one of the exact same type, which took me ages, and the fault remained!
I also did everything else first from the forums, checked all wiring, ground strap, dashboard warning bulb, battery ground etc. Nothing fixed it.
The exact fault in the end was this:
- The assembly holding the brushes (which includes the rectifier) seemed to be mounted so one of the brushes was very close to midline of the two slip rings so it was almost crossing from its slip ring to contact the slip ring for the other brush. If you look at the images you can see this.
The solution was this:
- I put two 2mm spacer washers between this assembly and the metal top plate mountings for it as in the photos then reassembled it. This moves both brushes very slightly towards the front of the car so they now rub along centres of the copper rings they connect with, not the edges!
It is a shame it took so long for me to find this fault. I have not seen it described before which is why I am putting up here, especially as this product seems to be very commonly available.
You obviously do this modification at your own risk and I cannot guarantee that it will work for your fault nor can I say how long it will last. However for me, based on the evidence of the off-centre wear on the copper slip rings, it seemed to be the best solution and so far seems to have fixed the problem.
