My problem resides with my 85 300DT. Tonight, I parked it in the garage, turned it off, removed the key and WHAT????? The battery light stayed on.

After doing a four page search, I disconnected the glo relay (no luck....light still on), inspected the wires going to the compressor (disconnected them and light is still on), finally pulled off the neg battery cable. Light went off.

I'm going out right now to hook up the battery and measure the draw vs. the draw with it unhooked. Then I'll start it and measure the voltage to see if the alt is charging.

ANY IDEAS?????

Thanks in advance

Don

__________________
DAILY DRIVERS:
'84 300DT 298k (Aubrey's)
'99.5 Jetta TDI IV 251k (Julie's)
'97 Jetta TDI 127k (Amber's)
'97 Jetta TDI 186k (Matt's)
'96 Passat TDI 237k (Don's
'84 300D 211k Mint (Arne- Undergoing Greasecar Conversion)

SOLD:
'82 240D 229k (Matt's - Converted-300DT w/ 4 speed

To me it sounds like the key "ignition" switch. I saw a problem just like yours in a friends 240 and that's what it turned out to be.
Good luck, Adam

Hello Don
I am guessing blind: disconnect the alternator.
I have seen three MB alternators that shorted internal, symptom was the same.

bad alternator and or voltage regulator.
good luck,
spo out

Thanks for all the replies. You guys have been there and done that.

It was the alternator. Unplugged it and the light came off. Put a new VR in the back and still, it didn't come above 12.5 volts even when running.

Am going out to heat the garage now. I don't like replacing alt's. Need to buy 10 more gallons of hand cleaner.

Thanks again,

Don

__________________
DAILY DRIVERS:
'84 300DT 298k (Aubrey's)
'99.5 Jetta TDI IV 251k (Julie's)
'97 Jetta TDI 127k (Amber's)
'97 Jetta TDI 186k (Matt's)
'96 Passat TDI 237k (Don's
'84 300D 211k Mint (Arne- Undergoing Greasecar Conversion)

SOLD:
'82 240D 229k (Matt's - Converted-300DT w/ 4 speed

It was a little different though. When I shut the engine off the alternator light was off when its usually on. When I took the key out it came on. This happened at the first fuel stop of a weeks camping vacation (had to do more hiking than driving.) It turned out to be a shorted diode in the rectifier. It was a Bosch alternator out of a Peugeot diesel that, it turns out, thanks to a local car electric shop, to be the same as a Porsche and cost $30