300tdi intermittent battery light flashing on and off?

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Originally Posted by LR1953

G'day all, I have a similar problem with my '98 300 Tdi. Occasionally, the warning lamp glows faintly, so faintly it's hard to detect in daylight, but noticeable at night. Battery voltage doesn't seem to drop however. More likely to occur when everything's warmed up, or say at the top of a steep climb at say 40 KmH. I'll check earth connections as suggested in this Thread, but I'd like to hear from anyone else who's experienced this problem.
Cheers, Rob S

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An excitor diode going open circuit can cause the light to glow dimly. The alternator will otherwise work properly.

Aaron

When this happened on our D1 we found the connection to the alternator was okay, but the alternator was failing. New alternator fixed it.
Is your tacho playing up? From memory it also comes off the alternator.

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Originally Posted by dromader driver

Had this with a failing alternator. brushes/commutator

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the light coming on dimly has 2 common causes IME

1. as mentioned the brushes lifting off of the slip rings in the alternator,

2. corrosion in the fuses that drive the alternator excite circuit and ignition side.

there are some other less common ones and of the less common ones the excitation side of the internal voltage regulator blocking diode is common BUT its failure is usually caused and masked by a failing regulator pack diode.