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Re: 79 MGB Roadster Alternator Problems

To: John c Kahoon <john.kahoon@juno.com>
Subject: Re: 79 MGB Roadster Alternator Problems
From: Art Pfenninger <ch155@freenet.buffalo.edu>
Date: Fri, 4 Sep 1998 13:28:07 -0400 (EDT)
On Wed, 2 Sep 1998, John c Kahoon wrote:

> My generator won't charge a dead battery, it has field windings, and
> unless you put
> 12volts to the windings, it only puts out 1.5volts.
> Do use a good battery for checking gens./atls. and save yourself some 
> aggravation.
> Does anyone know about voltage regulators ? I have a 71 midget with a
> generator,
> the regulator has three coils that are adjustable. I'd like to know what
> each is for, and
> how to set them ( gen light comes on at an idle since I cleaned the
> contacts )
> 
> john.kahoon@juno.com
> 71 midget

***The three coils are the cut out relay on the left, the current
regulator in the middle and the voltage regulator on the right. The 1st
coil to operate is the cut out relay on the left side of the voltage
regulator.Its purpose is to connect the generator to the battery once the
generator is putting out enough current. When the engine is first started
all 3 coils have their contacts closed, the condition of the battery
determines  which
of the other 2 coils open next. If the battery is low, and the charging
requirements are high (heater, radio,lights on) then the next coil to open
will be the current regulator which is the center coil. The current
regulator serves as overload protection for the generator. Without it the
generator would continue to produce current to satisfy the weak battery
and end up overheating itself. The current regulator opens and closes its
points which in turn interrupts the generators field circut which in turn
limits the current the generator is able to put out. As the battery
reaches its charged state the voltage regulator, the coil on the right,
comes into play. Its electro magnetic field causes the contacts to open
which puts resistance into the generators field circut. This now limits
the generator voltage which causes the current to fall. When the current
falls the current regulator, the left coil, loses power and its contacts
close, remaining closed until the generator starts putting out too much
current for its own good at which time the points open and the whole
process starts all over. As far as how to adjust the unit, the directions
are in the manual but I wouldn't recommend it unless you are sure of what
you are doing.
...Art
 


> 
> On Wed, 2 Sep 1998 07:37:16 -0400 Chris Kotting <ckotting@iwaynet.net>
> writes:
> >Rule #1 of alternator diagnosis:  Never try to diagnose a potentially 
> >sick 
> >alternator with a flat (or potentially sick) battery.  Borrow a known 
> >good 
> >battery from another car if needed.
> >
> >Contrary to some folks belief, an alternator will not charge a flat 
> >battery.  A generator will (because it uses permanent magnets) but an 
> >alternator won't (because it needs battery voltage to energize a set 
> >of 
> >electromagnets).
> >
> >Chris Kotting
> >ckotting@iwaynet.net
> >
> 
> 


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