Gen. not charging

[Bruce Parker (RIP)]

There is a section in the Chev MB-C2 manual that talks about reverse polarity. It says that "if the polarity of the generator is reversed the circuit breaker contact points will vibrate and burn". Ii goes on to say how to polarize the regulator by momentarily connecting the GEN to the BAT terminals.

What's not clear is how the generator finds itself with a revered polarity. I expect 'new in the box' will most likely be correct...I say this because for the first two 6 volt negative ground systems I installed years ago (MB jeep and C-15A), I was completely unaware polarity even existed. It only came up when I was figuring out the differences between positive and negative ground systems when I bought my first Ford.

Originally Posted by Lynn Eades

Bruce, If your generator is not "polarised' the cut out points stay closed when you turn the ignition off. (the two brush geny has a cut out in the regulator)
The result of this is that the generator is "fed" by the battery. The generator in this situation tries to (be a) motor. The "motor" cannot turn because the fan belt stops it. The end result is that the "motor" (generator) burns out.
Not much noise, but a bit of smoke!

If David's geny was charging, at all, the ignition light would go out.(or at least would appear so) I have no experience with adjustment of the brush in a 3 brush geny, but I would expect it to still put out a some sort of charge, not none at all
A geny that "motors" will usually be o.k.
I would expect the fault to be the cut out, a wiring issue, or an earthing issue.
If the geny is removed to an auto electrical shop it can be tested.
The big wire on the generator is the one hooked to the battery. The little one goes to the cut out.(the cut out only has 1 wire????? The other side goes to earth on the case???
Have I got that right?

In a three brush generator the third brush controls the voltage to the field windings and so the strength of the magnetic fields) The strength of the magnetism from the fields is what dictates the output voltage of the generator. I hope these snippets help, David.