[Vwdiesel] Alternator testing tricks?

Shawn Wright swright at zuiko.sls.bc.ca
Sun Nov 13 14:07:20 EST 2005

Thanks for the troubleshooting tips. In this case, I didn't need to look
to far - the problem was a loose nut on the alternator! Charged battery
overnight, resting V was 12.7V. Started right up, and alternator light
went out at ~1000rpm. Voltage is steady at 14.3V from idle to 3000 rpm. 
So I think I'm ok, hope I didn't damage the battery too badly. I will run
my spare and leave the other on charge until the hydrometer says it's ok.

btw, anyone have a source for just the brushes? I have several good voltage 
regulators with worn brushes. Last time I bought a reg, they were about $14, now 
they are at least twice that! I'd like to try replacing some brushes. 

On 12 Nov 2005 at 20:11, Sandy Cameron <scameron at compmore.net> wrote:

> At 04:50 PM 11/12/05 -0800, you wrote:
> >The last two drives on my '88 Westy TD have resulted in a slow starting 
> >battery. Today, it was a no-starting battery. Luckily, I had thrown a spare
> >battery under the seat. Back home, I checked the battery with a hydrometer -
> >all cells were equally low. It also didn't seem to recharge much at all after
> >1/2 hr driving, so I suspect the alternator. Aside from the obvious
> >regulator/brush assembly replacement, what other tricks are there for
> >diagnosing a worn out alternator? The alt light goes out right away, and has
> >never flickered at all.
> That may indicate the alternator and regulator are OK, but it's not
> commected to the battery.
> Look for obvious broken lugs or cable from alt output to wherever it
> connects to Batt+
> If the light comes on when the key is turned , the reg is drawing power, the
> brushes are probably ok. The light goes out when you rev the engine, the
> regulator is working and the diode triple feeding it. Now all that's left is the
> main diode bridge and the wiring that carries the juice to the battery.
> Double check the grounds too, always were a weak point.
> I dont trust the ground return thru the block. I added a lug to the back of the
> alternator and ran a heavy ground wire from that to the neg batt term.
> Sandy

Shawn Wright
'85 Jetta D 
'88 Westy 1.6TD 5 speed
 (see progress at http://members.shaw.ca/vwdiesels)
'82 Diesel Westy

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