I have a 1980 300td with a WVO conversion. I bought an upgraded 80 amp alternator exactly a year ago and noticed that the battery light is always on. It's very dim sometimes and bright other times. I checked for battery drain by disconnecting the neg terminal and putting a test light between the terminal and cable and there is no draw until I turn on my fuel switch solenoid. So that wouldn't be the draw since it's off when the car is. I checked the glow plug relay with the car off and there is power going to it. There's power on both sides of the large metal fuse and the screw beneath it even when the car is off. Is this normal? I'd think that the power would be off to it when the key is in the off position. Any input would be greatly appreciated.

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2022 Nissan Frontier Pro4x
1990 Mercedes 420SEL
1950 Packard 8

Previous German cars-
2001 Mercedes SL500
1983 Mercedes 300SD
2011 BMW 328i (manual)
2008 BMW 535xi (manual)
2006 BMW M3 (manual)
1980 Mercedes 300TD
2006 BMW 750i
1996 Mercedes E300D
1994 BMW 740i
2006 BMW 330xi (manual)
1999 E300DT Smoke silver/black 253k
2012 BMW 535i Xdrive M-Sport
1984 300TD-T 304k
1988 Mercedes 560SEL (parts car)
2010 BMW 550i xdrive
2017 Audi A4 Presitge
1979 300SD 313k
2003 E500 189k