On my 1985 300DT I have replaced:

1. The voltage regulator
2. The alternator
3. The battery

I still have the same problem. It won't charge. While running, the voltmeter indicates about 12.4 and the battery light stays on.

What else could it be but wiring? Any ideas before I tear the wiring apart?

Thanks

Don

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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

Sounds like a broken circuit = broken wire or the charge light diode is dead.

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1985 300SD
1983 300D
2003 Volvo V70

https://www.boldegoist.com/

Check the distribution block just in front of the battery on the passenger side fender. I was diagnosing a similar problem and found that one of the connections was loose... ended up replacing the voltage regulator before I found this.

BTW, I've heard you should charge your battery overnight before using your motor/alternator to recharge a fully drained battery. Something about very high loads for the voltage regulator potentially causing damage. I'm not sure if there is any truth to this but better safe than sorry.

Good luck!

-John

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1985 MBZ 300DT
1969 MBZ 220d
1984 MBZ 300TDT
1981 VW Vanagon

I changed alternators twice, recently, when I had charging problems. Eventually, I ended up with a good unit.

A severely discharged battery is a major load (heat) on the rectifying diodes in an alternator. With a rebuilt unit, this may cause problems since they may be marginal.

Does your charging voltage vary at all? It should be a little higher at start up then decrease gradually to a constant level as the battery recharges.

__________________
Sam

84 300SD 350K+ miles ( Blue Belle )

These are helpful suggestions and I appreciate your input.

I'm going to attack the wiring first after a conversation with Roy Hunter and then go from there.

Thanks again

dp

__________________
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

In the event of future searches on the topic, my problem was a wire that was shorting out between the alt and the distribution center on the passenger side. Blew through a bunch of voltage regulators before I found it. Thanks to the forum for its help

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