Paul,
Before you go tearing too many thing apart let's go over your test results.
>> The Volt Meter easily rises to +14 - 14.5 volts, when the car is
first started from it's initial 12 volts. While the light is off, the Amp
Meter will show a charge rate or roughly 3 - 5 amps. When the battery gets
to 14 volts, ( a minute or two) the light comes on, and I'll see no current
flow on the amp meter.
A fully charged battery is 12.72 V (excluding surface charge) there is a
certain amount of resistance in each cell of a battery about .2V. To fully
charge a battery you must have a voltage above 12.72 + (.2 X 6) = 12.92 V. If
a battery is discharged it requires less voltage to charge it, as the battery
reaches a fully charged state more voltage is required to keep charging it.
The reason you are seeing no current when the alternator gets to 14 volts is
that the battery is fully charged. No more current is required to charge the
battery. Normal voltage from an alternator is considered to be in the range
of 13.5-14.5 volts.
>>Conditions: Starts quick and easily. All ace. turned on, only drops the
voltage a max. of 1 volt. (with the idiot light on or off)
Doesn't sound like a bad battery or alternator to me. <G>
>>QUESTION #1: Do I suspect the battery, alternator, or something on the WHT
ckt. that is loading down the line.
>From you test results the battery is OK, and the alternator is putting out.
There may be problems in the circuit for the warning light.
>>QUESTION #2: If it's the alternator, would it be the brushes? regulator?,
diode array?
Brushes I don't think so. Regulator possible, I'm not that familiar with how
B alternator systems are wired (hey mine has a C40 on it). Diode array is a
possible. Here is a simple test for bad diodes. Put an A/C (yes A/C)
voltmeter across the battery terminals start the engine, headlights and heater
fan on. rev the engine to about 2000 RPM. Read the voltmeter. If you
reading is less than four-tenths of one volt your diodes are OK. In your case
I would repeat the test when the warning light is on.
>>QUESTION #3: Could the battery being at 14.5+ volts, make the alternator
think it's not charging, so the light comes on, since the alternator output
voltage is the same as the battery voltage?
Assuming no voltage drops in the circuit, alternator output is the same as
battery voltage. Now before you hit the flame on button let me explain.
Let's say your alternator has an output voltage of 14.0 volts, measured at the
back of the alternator. Then when you measure the voltage at the battery you
will see 14.0 volts, assuming no voltage drops (resistance) in the circuit.
If the system is at 14-14.5 volts the alternator is charging what the battery
needs. If the battery is fully charged, a system voltage of 14.5 and zero
current into the battery would be normal.
Another way to check the state of charge of you battery is to let the car sit
over night after driving with all electrical systems off. Then in the
morning, before turning anything electrical on, measure the voltage across
the battery terminals.
12.6 Volts or above indicates a fully charged battery.
12.4 volts is 3/4 charged
12.2 volts is 1/2 charged
12.0 volts is 1/4 charged
If you measure you battery tomorrow morning at 12.6 you do not have a charging
system problem, you have a problem with the indicator light circuit.
I hope this helps,
Rick Ewald
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