Re: Giulietta Bosh Generator.

[Simon Favre <simon@domain.elided>]

Positive ground is a myth. Polarizing a generator is a myth. You polarize
it every time you turn the ignition on. There are no permanent magnets in
a generator. The regulators on these cars, both Bosch and Lucas, are only
relays. There are no permanent magnets in the relays either. The way it
works is this: When you turn on the key, the battery provides power to both
the armature and the field of the generator through the charging light.
When you start the motor and rev it up past a certain point, the generator
is putting out more voltage than the battery. At a trip point determined by
the regulator (relays), the regulator connects the generator output (the
armature) directly to the battery. This shorts out the charging light.
When the voltage rises to a second trip point, the regulator starts chopping
the field coil to reduce the generator output to prevent overcharging. The
default mode of the regulator is to ground the field terminal through the
overvoltage relay contacts. When the max voltage is reached, these contacts
open up, taking away the field current. This causes the output voltage to 
drop, which makes the regulator close the contacts again, etc. etc. etc.
There's also a resistor across the overvoltage points, so the field isn't
completely cut off, but the field current drops way down.

The key point here is that Alfa, in a fairly smart move, specified that all
the instruments on Giuliettas work in +ve or -ve ground. The generator and
regulator don't know the difference. It's really as simple as reversing the
battery. Your problem may lie with either the regulator (if it's Lucas,
that's a given), or the wiring. Note that if the generator light does NOT
come on when you turn the key, the generator will NEVER start charging!
Double check the wiring against a schematic, and make sure the generator
light functions properly. My advice is to scrap the Lucas regulator and
put in a decent Bosch unit. You can use one from a Porsche 912. The early
105 cars with a generator had a Bosch regulator that is more correct. The
only difference is the shape of the terminals. The Lucas had screws you 
stuck the wire in, so you have to add some terminal connectors either way
if you put in a Bosch regulator. 

Data point: My '62 had the Lucas crap in it at first, too. I switched the
battery and had a Lucas generator happily putting out -ve ground before I
replaced it all with Bosch. I had a Lucas regulator go bad and burn out a
perfectly good generator. Bosch is the way to go.

Dr Andrea Berardelli wrote:

>Dear Fellows,
>hope you are all having a great summer.  I am, the Giulietta is almost done 
>and it looks great,  it is a really nice car to work on, highly recommended,
>Anyhow, the car is a 1300 normale of 1962 vintage.  As such is had a Lucas
>generator and it is positive ground.  The Lucas generator has been replaced 
>with a Bosh unit, just rebuilt.  The problem is:
>This generator does not charge.  I am sure all the connections and wiring are 
>all right, I think I should "Energize", "polarize" the unit for positive 
>ground as I am sure the rebuild  shop did it for negative ground.
>The question is, how do you do that?  I have done it for my Land Rover but I
>cannot remember how.

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