A bad alternator?

[willmagrath]

Hi all,

Van was fine, drove it 30 miles no issues and then has repeatedly started well whilst sat and we've been working on it.

We then left it idling the other day to circulate new oil. Turned it off, left over night and then battery was dead. Have checked the alternator with the multimeter on the battery, it's 12.6v when off but drops to 12.1 when running...

Should that happen?

Thanks

[R0B]

Test the voltage at the alternator. It could be a faulty voltage regulator. It's an easy job to change.
VW Voltage Regulator - Alternator / General Use / 14.5v

[Oldiebut goodie]

Is the alternator light glowing and then going out when the engine is started? If not check that the blue? wire is connected at the alternator. You have to excite the alternator with voltage via this to get the alternator to work.
( I need a dozen wires to excite me and make me work  )

[TwinTurbo]

if it's actualy draining the battery then the rectifier has probably failed.