Dodge Stratus: Battery Light ON!

96 Dodge Stratus 2.4L. Battery light comes on every odd trip, perhaps every
2nd or 3rd time we take the car out. The dealer was made aware of the
problem a few weeks ago and replaced the drive belts - they were really
worn.

Now the light still occasionally comes on. If I immediately go to neutral
and turn of the ignition and restart the engine, the light goes out again
and stays out - for a good while, perhaps the entire trip.

Any ideas? Is this for sure a bad alternator? If the belts are new and the
alternator was bad why is the problem so intermittent?

-Vince

 

There should be a trouble code set if there is a charging system
problem. See what the computer "thinks" is wrong.

But even that won't give a complete diagnosis. You need to determine:

a) is the alternator producing sufficient current at the correct voltage
and the light is a false warning
b) if not, is the alternator field receiving the proper excitation
current from the regulator (inside the computer).
c) is all wiring intact, and are all connections good?

The following tests should be done when the warning light is on:

a)Put a voltmeter on the battery with the engine running. It should be
in the neighborhood of 13.6 volts (no electrical loads turned on) and
shouldn't drop more than a tenth of a volt or so when you turn the
headlights on. Furthermore, the voltage should come back up if you rev
the engine slightly. You can also remove the alternator and have it
tested at an auto parts store, but this test is nearly as good.


b) if the alternator fails test "a", then check the field terminal
voltage at the alternator with the ignition in the "run" position
(preferably with the engine running, but be careful of moving belts and
spinning pulleys). If its getting battery voltage there, then its most
likely an internal alternator problem, OR a wiring problem between the
alternator and the battery. To rule the latter out, shut the car off and
measure the voltage at the large "Bat" or "B+" terminal on the
alternator. It should read equal to the battery voltage. Ideally, you
should also clip a test lamp there because high-impedance voltmeters
sometimes will read normal voltages across very bad connections, but
current won't flow when a load is applied.

c) if it comes to it, trace the wiring out.

 

Sounds similar to my 93 Caravan 3.3 (now fixed). Intermittently, over a
period of a couple of months, rarely at first, more often towards the end,
the Battery light came on. When a restart would not correct it, I found a
slight tap in the alternator connections would do the trick. It made me
think at first there was a bad/dirty connection at the alternator. Cleaned
them all up, but problem persisted. Toward the end it was happening, as you
mention, every, or every other trip, and tapping alt to restart output was
getting more severe. When battery light was on, code 41 (Generator field not
switching properly) was active. All tests on alternator when code was not
active and Batt light not on were normal, volts and amps output in limits.
When code was active and Batt light on, alt had 0 output.

Alternator replaced - no problems since, 5 months ago.

 

Probably just the brushes. When they get worn down pretty far, their
springs don't hold them tightly enough against the slip-rings. You can
replace them in a Nippondenso alternator with a phillips screwdriver.
They cost about $10.00 from an alternator rebuilding shop.