In that case I would clean the contacts on the three (or two) relays with a
contact file or wet and dry. One of the relays has a normally open contact
and this is the cut-out which connects dynamo output to the battery to
charge it. It should operate when the dynamo voltage is slightly above
battery voltage, between 12.7 and 13.3v. It should drop out when the
voltage falls to between 9.5 and 11v. The voltage regulator should operate
when the system voltage rises to between 14.9 and 15.5v at 50F, lower at
higher ambients. The voltage regulator works by inserting a resistance in
the field circuit, which drops the output voltage. This causes the relay to
release again, removing the resistance, the voltage rises again, the relay
operates again, and so on. So effectively the relay is operating and
releasing very rapidly, or buzzing. You should be able to see a small blue
spark between the contacts if you look at from the right angle, and feel it
vibrating if you lightly touch the armature with a finger tip. When you
first start the car the relay may not be operating until the charge lost by
the battery during cranking has been replaced. Then the relay will start
buzzing, but be operated for a short period in relation to the length of
time it is released, still charging the battery but at a slightly lower rate
than before. As the charge on the battery rises the relay is operated for
longer relative to the time it is released, gradually reducing the charge
rate, until things reach an equilibrium. The third relay, if you have one,
is the current regulator, only on later versions. This should only operate
if the load from the electrics rises above about 22 amps to prevent damage
to the dynamo. It does much the same thing i.e. introduce a resistance into
the field circuit and reduce the dynamo output, at which point it is the
battery that is carrying some of the load and the system voltage will start
to drop. If either the voltage or current regulator contacts are dirty and
giving a bad connection you will get reduced, and possibly varying, output
from the dynamo.
PaulH.
----- Original Message -----
From: "Simon Matthews" <simon_atwork@hotmail.com>
To: <paul.hunt1@blueyonder.co.uk>; <mgs@autox.team.net>
Sent: Monday, January 19, 2004 11:19 PM
Subject: Re: Bench testing regulator
>
> Paul,
>
> I checked the generator already using that procedure -- it seemed to be
OK.
>
> Simon
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