Re: Diagnosing Battery Discharge

[bearbvd@domain.elided (Greg Hermann)]

At 7:12 PM 3/5/00, Kevin Trent wrote:
>Last fall my '73 spider developed an electrical drain that will discharge
>the battery overnight.  I used my  multimeter to measure the drain and found:
>
>1.  a drain of about 3 amps (I think - if I read the scale correctly).
>2.  removing each fuse in turn had no effect on the drain.
>3. disconnecting the big read wire to the alternator from the battery
>eliminated the drain.
>
>The alternator has been rebuilt in the past and now incorporates a small
>"transistorized" voltage regulator mounted on the back of the alternator.
>This eliminated the standard regulator, and makes the alternator a "one
>wire" unit.  Despite the drain when shut off, the alternator charges at
>14.5volts when the engine is running.
>
>My question:  Can my alternator and/or its now integrated voltage regulator
>have some internal short that is causing this battery drain?  Or is my test
>logic and diagnosis faulty?
>
>Thanks,  KCT,  Powell, Tennessee   (where its been sunny and 70 for two
>weekends...)

Your logic sounds fine. The 3 amps sounds suspiciously like the field
current that the rotor of the alternator would draw, and it would thus
appear to me that the regulator is putting full battery voltage to the
field when the engine is shut off.

Regards, Greg

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End of alfa-digest V7 #1419
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