Nick,
The amp meter only tells you whether current is flowing into (+) or out (-)
of the battery. It tells you 3 conditions:
1. Normally, when the battery is slightly discharged (after starting or
idling with a heavy electrical load), when the engine rpm increases the amp
meter will show a good + charging rate.
2. When the battery is fully charged and the current rate returns to just
above zero.
3. If the loads are heavier than the generator can handle, you get a
negative flow on the amp meter. This is not good for a long period of time,
so either increase engine rpm or decrease the load. At a stoplight and with
a slow idle, with the ignition and brake lights on, it is normal to show a
slight discharge.
A voltmeter tells you the voltage of the system.
1. With the engine off, a fully charged battery should indicate around 12.6
to 12.8 volts. This may be slightly higher for a short period after shutting
off the engine.
2. With the engine running above an idle and a fully charged battery, the
system voltage should be around 14.0 to 14.5 volts with a light load, with
15.0 volts max. If the battery is deeply discharged or a heavy load, the
voltage may be lower.
3. The nominal charging voltage of our cars is 14.58 volts at 70 degrees.
In the case of your 56 plym only charging about 12.8 volts at high rpm, you
are not getting any significant charge. The best advice is to replace BOTH
the generator & regulator, since either can cause the other to be damaged.
And as Bob said earlier, brushes may cause problems at rpm if they are worn
out (low spring tension) or sticky. You might inspect these first.
And advice for EVERYBODY else: I highly recommend voltage regulator fuses.
These are small blocks that mount on the voltage regulator terminals. You
can get them at NAPA under a P/N like VRF30. Very cheap insurance. If your
battery, or regulator, or generator shorts out, what happens: the wires
between them get melted from the overload and may start an engine fire,
possibly resulting in the loss of the entire vehicle.
Dave Homstad
56 Dodge D500
-----Original Message-----
From: Forward Look Mopar Discussion List
[mailto:L-FORWARDLOOK@xxxxxxxxxxxxx]On Behalf Of Bob Moore
Sent: Tuesday, September 08, 2009 8:06 PM
To: L-FORWARDLOOK@xxxxxxxxxxxxx
Subject: Re: [FWDLK] Generator or voltage regulator
Hi Nick,
Watch the voltage over time, and see if it is gradually climbing- if you
just started it with a low or maybe even a normal battery this could be ok,
but eventually it should head up to ~13.8.
I used to play games- first see what happens when you change the load, like
turn on the headlights and the blower and see how it changes. Then you
could try disconnecting the battery while it is running (disconnect your car
stereo or other solid state devices before trying this one!) and see what
happens to the voltage, the other fun thing is to try closing the relays
with your finger tip with the fan belt off, you should be able to get the
generator to 'motor.'
If the brushes are worn out, the current & voltage output will drop off to
near 0 when you accelerate. Current/amps in my mind is the ability to drive
a load, voltage is just the open circuit potential, you can still have
voltage with no load but it might go away when you apply current (load).
Watts is Volts * Amps, or ability to deliver a heat/work load etc.
Have fun!
-Bob
-----Original Message-----
From: Forward Look Mopar Discussion List
[mailto:L-FORWARDLOOK@xxxxxxxxxxxxx] On Behalf Of Nick Sperduto
Sent: Tuesday, September 08, 2009 4:10 PM
To: L-FORWARDLOOK@xxxxxxxxxxxxx
Subject: [FWDLK] Generator or voltage regulator
I can't find my shop manual it's misplaced somewhere in my mess of a garage.
My 56 plym is only charging about 12.8 volts at high rpm.
Is there an easy way to tell if it's the generator or the voltage regulator.
Thanks,
Nick
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