Here's more on generators and polarity from a page that I've been working on.
Regulator Polarity
Regulators are not interchangeable for use on either negative or
positive ground systems. In addition, the charging system maximum output will vary
between makes and models of vehicles. Different regulators are used with the
different generator ground systems. It is essential that the regulator be
specifically designed for the particular electrical system it is to be used with.
When the regulator contact points are vibrating (operating), there
will be a slight arcing, regardless of the use of absorbing resistors.
The arcing, although slight, will create enough heat so that there will be a
small spot of molten metal between the contact points each time they separate. The
usual tendency is for the molten metal to stick to the positive contact point so
that a build-up of metal will occur on the positive contact point and a crater
will result in the negative contact point. To help overcome this condition to some
extent, the negative contact point is made of a different material than the
positive point. When electricity flows through the contact points, in the proper
direction, the transfer of metal between contacts is thereby kept to a minimum. If
a regulator for one polarity is installed in a charging circuit designed for the
opposite polarity, the electricity will pass through the contact points in the
wrong direction and shorten the life of the contact points considerably.
Polarizing
This points up the importance of polarizing the generator before starting the
engine, if there is any chance that the generator polarity may have been reversed
during the process of servicing. Polarizing the generator is the passing of
electricity through the generator field coils. Before a generator can be polarized
you must determine if the generator is EXTERNALLY or INTERNALLY grounded. If
service information doesn't specify the only other way to tell is to check the
connections inside the generator. If there are two wires (field and armature or
brush) connected to the armature terminal then the generator is EXTERNALLY
grounded. If there is only one wire then the generator is INTERNALLY grounded.
In the case of the generator with an externally grounded field, ground the field
terminal. Momentarily connect a jumper wire between the battery and generator
armature terminal. This permits a momentary surge of current to flow through the
generator which correctly polarizes it. With an internally grounded field
generator, disconnect the wire attached to the generator field terminal, and
momentarily connect a jumper wire between the generator field terminal and the
battery.
Buzz
-------------------------------------------------------------------------
On Mon, 07 Aug 2000 12:39:22 -0400, you wrote:
>>you must *momentarily* connect a jumper lead between the
>>generator terminal (usually marked GEN) and the battery terminal (usually
>>marked BAT) of the regulator *BEFORE* starting the engine. The momentary
>>surge of current (via the jumper) will correctly polarize the generator.
>>This problem does not exist with an alternator, but only generators.
>
>I thought you "flash", momentarily connect a jumper lead from, the FIELD to
>the
>battery ungrounded terminal. This assumes that the field return line is
>grounded,
>usually an internal generator connection.
>
>?? Yes ??? No ??
>
>Ted H.
>
>
>
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This archive was generated by hypermail 2b29 : Sat Sep 02 2000 - 09:32:25 PDT