[Vwdiesel] Chuck's Charging problems

[HWY9FERGS@cs.com]

Chuck Said:    

Subject: [Vwdiesel] Charging Problem

My '84 is running great but I can't figure out why the battery isn't
getting a full charge.  After about a week of driving the battery will
gradually lose it's charge (quicker if driving at night with lights).
I've cleaned grounds, checked for continuity.  The alternator is a Bosch
reman putting out 15 volts at the connector.  After the connector it
immediately drops to 11 or 12 volts depending on the load.  When the
lights are on it drops to 11.8!  After a bunch of testing and cleaning
of terminals and grounds I now have the battery light staying on more of
the time than before.  Any suggestions?       Chuck Carnohan

Hi all, Ferg again, This is a PERFECT time to check with a voltmeter to find the exact spot where you have the bad connection.  First, set your meter to read voltage in the proper range 12v.  Put your negative lead on the positive alternator LUG (the lug itself, not the terminal).  Take the positive lead and touch it to the  terminal surrounding the pos lug.  Not reading any voltage?  It means there's no problemo with the first connection!  Same thing with the main battery connectors. Usually if there's a clean tight connection there, you won't have a problem, but sometimes the connection can be compromised enough to cause it to break down under load.  That's typically what's happening when you're having troubles starting the car, the ignition lights go on normally when you turn the key to "run", but as soon as you turn to "start", you get a click and all goes dead-no cranking.  A more insidious cause of voltage drops can be in the crimp type connections. Just because a wire is joined together doesn't mean there's no resistance.  That's what we're looking for here. Going back to our travels with the meter, with the car running, keeping the negative lead on the positive alternator lug, you move the positive lead on down from point to point on your cable or wire . Every time you go to the next section (after any connections or crimps) if there is a problem with the connection, that's when you'll see voltage. When you see voltage on the downhill side of a connector, but not on the uphill side, that connector is where your bad connection is.
You can also just put you Neg lead to ground and read the voltages along a live circuit until you see a lesser voltage after a connection.  That works too.  It sounds like that's what Chuck did at the alternator connector. And if it reads fine on the lug (15 volts) but low on the wire right after the connector, it has to be the crimp on the connector for the cable going back to the starter.  While it's running try jumping in piggyback from the alt lug to the main starter lug (where the questionable cable runs) and see if your battery charges?  Very curious what you'll find.. I'd be willing to bet you need to r&r that alternator cable (or crimp a new terminal on it).  Doug Ferguson