[T2] alternator/regulator fault?

[Robert Mann]

My charging deficiency, as evidenced by the red discharge light, has now
taught me several lessons applying beyond my 1600dp.

The case went:–

1  As previously reported, discharge light would not go out <2100rpm, and
then would come back on when returned to low revs.  Net discharge at
cruising was evidently just OK  -  a hundred miles cruising led to neither
severe discharge nor a fully-charged battery.

2  Autoelectrician had vehicle an hour or so, concluding fault was within
alternator (could be regulator, which in this sub-type is within the
alternator).  David Raistrick sooled us onto a v g exploded drawing of the
alternator; the regulator is a small 'vertical cylinder' enclosed in the
alternator housing near the fan end.  The same set of guidance from David
allowed us to view a colour pic of a v different-looking device which
someone called 'alternator brushes', a term I haven't heard and suppose
spurious (a main reason why it was progress when Plymouth {1962} & Renault
{1966} supplanted the generator by the alternator was to end use of brushes
– which VW finally caught up with in my '73 T2).

      The regulator of charging systems based on an alternator so rarely
gives trouble that I knew not where it was, let alone what it looked like.
 {"Nostalgia": the regulators of generator-based charging systems, with
soft-iron L-'levers', arcing points, etc gave trouble so often we all knew
what they looked like – and cursed them, muttering 'Lucas the prince of
darkness' or similar.}

 3    The instructions in the Bentley for removing the alternator looked
unforbidding, but we soon concluded as David R had warned: the easier route
for removal entails dropping the engine.  Unlike *real* VW home mechanics,
I have never dropped the 1600dp or any other VW engine (now there's a
confession – embarrassing or lucky), and was reluctant to start.

4    The 6-y-old battery can be charged to 13.5 V and readily cranks the
starter motor for many s. Charging on the bench with a computerised modern
charger, the first stage of charging is a desulfation mode (some type of
pulsing, as hinted by the display panel).  The battery was ultimately
charged by this fancy charger to 13.5 V, a figure which implies battery is
not too miserable.  Electrolyte when thus charged floats 2 balls in the
under-rated old hydrometer with 4 colored plastic balls.

5    The battery posts, esp the +, and more the clamps on those posts, were
found corroded and promptly cleaned.

6   The discharge light today failed to show at all, while engine started &
ran.

7   Not the little lamp, which tested OK on another base (*viz*. the oil-P
warning light base) but its base was the reason it had suddenly failed to
show.  The sliding contacts of that miniature base had become corroded &/or
shifted  –  and are not necessarily easy to fix.

8   The discharge lamp was again now ready to show with cleaned contacts in
its base.

10  The engine now started fine AND the discharge lamp went out c.200 rpm
and stayed out back at idle.  Thus, insofar as the discharge lamp can
indicate the performance of the charging system, all is well.

*11  Conclusion*: neither alternator nor regulator was faulty.
Autoelectrician could have merely cleaned the battery connections (posts &
clamps) and charged me for a new regulator and bulk h labour for the
surprisingly lengthy process of removal & re-installation of alternator to
get at the regulator.
     Most probably, corrosion at battery clamps on posts had built up
resistance which caused the charging light to indicate serious deficit in
charging at most revs.  BTW I'm almost certain the lamp when alleging
trouble was distinctly fainter even when showing its brightest, compared
with its brightness now; could that subtle dullness have been a hint of
high resistance in the charging circuit (at the battery)?

*Lesson implied:*  clean battery posts & clamps of corrosion; re-fasten
tight; then add petroleum jelly or grease covering posts & clamps, to
exclude corrosive vapours.  Do not infer defect in alternator/regulator
until you've done this humble cheap housekeeping.
      Also of course the experience implies a dashboard ammeter is
valuable.

Robt Mann
'73 1600dp Devon camper