My kid has a 1983 caprice that the battery goes dead. originally we thought
alternator was bad. when we put voltmeter on battery (12volts at rest) and
started car voltage dropped. we were expecting 13volts or so. we have
taken alternator in twice, two different shops and both said alternator
checked out o.k. upon further examination we found one of the spade wires
that go into a connector that attaches to the alternator bad. It would slip
out of the plastic connector. we were able to repair this connector (supply
of field voltage?) and then started car and voltage this time did not drop
and it read about 12.4 volts. we went to lunch and came back about 1hr
later and car started with no problem. (well almost no problem it is a
1983). voltage read just a little over 12volts but it was not dropping
below. (unless headlights were turned on and then 11.7volts). before my
kids car would not start even after 1hr of just sitting.
my kid tried starting car next day and battery completly dead.
my thoughts are something is staying on and draining battery. I think to
troubleshoot problem we need to get car started and let it run for a little
while charging battery. then turn car off and then remove neg cable to
battery and put meter in between to see if current is being drawn. if so
start pulling fuses and see if we can find culprit.
battery was replaced about 5 months ago. he pulled both alternator and
battery out and the parts store said both check out o.k. We even got a
second opinion on the alternator.
any other thoughts on my kids caprice classic woes out there? my kid lives
a little way out of town and works 6 to 7 days a week. so our trouble
shooting time is somewhat limited. any input would be helpful.
Look.. Check the battery draw when the car is not running. Make sure
some circuit is not draining the battery. You should not draw more than
maybe 50 milliamperes or so.
If you are drawing considerably more, then you have a defective circuit.
Possibly, if not probably, your old battery is toast by all this falderal..
Dont just guess and replace.. Diagnose and repair.
yes i agree on not guessing. it would of been easy to just buy another
altenator and still have the same trouble. I wasn't sure on what kind of
draw was acceptable when car was not running. thank-you for the info.
Have you checked the battery? How old is it? In spite of being able to
hold 12V, it may not have the power for anything else and it will not take a
charge. If more that four years old, I'd replace it. If less, I'd try it
in another car to see how it performs. Have you tried putting a charger on
Clearly insufficient, shows that there is low alternator output. This
could be a wiring fault.
Well, if the battery was not charging, that is not surprising.
Either self discharge due to a bad cell, or there is a parasitic draw
that is discharging the already very badly charged battery.
1. Put the battery on a proper charger, and charge it fully.
2. Measure the battery voltage, with it disconnected. Record this
3. Leave the battery sit for 12 hours, DISCONNECTED, and then measure
the (open) terminal voltage. It should be almost exactly the same
voltage as in step 2, above. If it is about 1 to 2 volts less, the
battery is defective.
4. Connect the CHARGED battery to the vehicle, with a properly
connected amp meter. Allow the vehicle to sit, doors closed, all
lights off, everything off (if the hood has a light, that is lit,
remove the bulb for this test. Measure the draw after 30 minutes, if
it is more than 50 milliammps (0.05 amps) then you have a high
parasitic draw, find and correct this problem.
If will not charge the battery if it is only putting out 12 volts. You
need between 13.6 adn 14.2 volts to properly charge the battery, and
that voltage would have to be maintained for considerable time (hours)
if the battery is in a state of low charge. You need a proper battery
Making sure to:
1. Wait between 20 and 30 minutes,
2. Ensure that all devices and lights (including the hood trouble
light) are off,
3. and then monitor the draw. If more than 50 milliamps, then there is
4. Remember: if you open the door, the dome light, and other systems
in most cars, will result in a large current draw, possibly damaging
the meter. Disable the door switch prior to making these tests.
Just because the battery was replaced five months ago doesn't mean it
has not failed. Also, it is clear from your voltage readings that the
battery is NOT charged properly. Put a proper battery charger on the
vehicle and fully charge the batter as described above. Run the 12
hour sitting test!
Get him a loaner car so you can properly diagnose the problem. That
will help greatly. Measure voltages at the alternator to see if the
alternator is in fact putting out the proper voltage.
Personally, I think both the alternator and the battery are probably
defective, but the wiring could also be an issue. (Don't say: we
checked the alternator, that and $5 will get coffee and a donut at
thanks for the input.
as far as measuring voltage at the alternator that may be a tall order.
from what i remember the lead connector is difficult to get to when
alternator is installed. however I did measure voltage from ground to
positve of battery and then from ground to lead that attatches to alternator
and obtained same voltage. (this done when car at idle and alternator not
installed). its just a short piece of wire.
What is the resoning behind waiting 20 to 30 minutes? if there is a
parasitic draw wouldn't it happen immediatly? sorry electronics background
not mechanic background.
I agree it would look like alternator and/or battery is defective. but
alternator was tested by 2 different parts stores. keeping in mind that
parts stores are there to make money. so i would assume that if there was
an issue with alternator they would have sold him a new one. and battery
what kind of tips are you leaving at dunkin donuts? or am i out of touch?
haven't been to a donut shop in years.
If it were my vehicle I would take it to a shop, that has the proper
equipment and the trained techs, to have the problem analyzed and the fault
corrected, rather than the hit or miss route you have been following.
A fully charged battery should read 12.67 volts.
Normal charging system voltage on that car is 14.5 volts.
(OEM voltage regulators did have some temperature compensation WRT
There are three connections on your alternator;
1) stud and nut is the alternator output terminal, it connects directly
to the battery.
2) larger red wire at two cavity plug is the voltage sense wire, it also
connects directly to the battery.
3) smaller (usually) brown wire is the turn on signal, its job is to
signal the voltage regulator to wake up and function, this circuit is
hot only when the ignition key is 'on'
(field current is supplied internally to the alternator thru the diode
trio which taps current off of one half of the stator)
If indeed the alternator is not the problem, you are missing voltage on
one of the above three mentioned circuits. Voltage available and
voltage drop tests will find the problem.
Both red wires are protected by fusible links located in the harness
that goes to the starter motor.
Good advice. Some more advice...if you do have to change out the
alternator, get a good one...perhaps from a friendly local alternator shop
or a top quality unit from a FLAPS. Some franchise stores sell some
pretty sorry rebuilt alternators with "lifetime" guarantees.
I have replaced a bunch of them.
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