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Old 09-30-2013, 11:50 PM
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Join Date: Sep 2007
Location: Long Beach,CA
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Quote:
Originally Posted by spdrun View Post
I killed the battery in my 240D a few weeks ago by leaving the interior light on when the car was parked for a month. Battery wouldn't hold a charge, so I replaced it with a Bosch group 49 unit.

Now I noticed (during a trip back from Boston!) that the alternator is charging a bit, but not enough -- the battery will discharge with the headlights and heater blower on. Max charge voltage seems to be about 12.5-12.6V. Also, the lights flicker quite a bit, and the voltage actually DROPS at higher RPMS (lights get dimmer). Turning off the heater blower and running the engine seems to allow the battery to re-charge enough to make the car able to start.

Do I need a new alternator or regulator? Could a defective battery be causing this symptom? All connections at the battery and ground-strap are tight; I checked. Charge warning light is only on with the engine off, as normal.

Thanks-
-s.
12.50-12.75 Volts is the Battery Voltage when the Battery is fully charged and ambient temp of about 75 degrees F. Meaning if there was any charging it was only keeping pace with the little bit of drain on the Battery after starting.

The Alternator will not work right if the Cables, Grounds and Wires are not in good shape and making good Contact.
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