Date: Thu, 28 Jan 2010 15:48:29 -0800
Reply-To: Alistair Bell <albell@SHAW.CA>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Alistair Bell <albell@SHAW.CA>
Subject: alternators, voltages, rebuild, idiocracy
Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed
Hi,
thought I would tell my tale of partial alternator rebuild and false
diagnosis, maybe others won't make my mistake :)
my '86 syncro has had an alternator whine, increasingly loud under
electrical load, for a few months now. Recently is has been getting
louder and after adding aux. lights I thought it best to fix it.
Measured voltage at alternator was around 13.5, at battery it was
13.4 or so. I thought this too low. Swapping some used, but within
wear range brushes didn't change voltage output nor eliminate whine.
Next step was to take alternator apart and check bearings. The slip
ring end bearing was dry, and a bit worn. I packed in some grease,
rubbed up the slip rings with garnet paper and put it back together.
Yes, I know, not a complete job, but at that time I didn't have much
time and I couldn't get pulley nut off to access other bearing.
Outcome was that nothing changed.
So when I had more time I took the alternator from my I4 westy
(parked), borrowed an air impact wrench (to get pulley nut off,
goodness how the impact wrench works like magic), and bought some new
brushes. Not a new regulator, just the brushes, $12 for the pair. I
wanted to try soldering in new brushes.
Also did some internet reading and found that bad diodes can cause
whining under load. That made me more convinced to just swap in my
known good alternator and play with the whining one later.
I took apart my spare alternator, cleaned connections etc, made sure
of solder connections too diode plate. Then I used a 300W soldering
iron to melt solder on regulator to remove brushes and solder in the
new ones. Some pics on this website shows how to do that http://
www.alfa-restoration.co.uk/alternator/alternator_rebuild.htm
The soldering was easy peasy, easier than I thought it would be. But
a good big soldering iron is needed.
When reg was out I checked that using procedure (outlined here http://
www.humanspeakers.com/audi/alternator.htm), using power supply, light
bulb and voltmeter.
"If you would like to test the functioning of the voltage regulator,
you will need a variable power supply that can vary from 0 up to
about 15 volts at about 3-5 amps, and a voltmeter. Attach "-" to the
connection under one mounting bolt hole and "+" to the tab on the
other side of the brushes. Set the voltage at zero and turn on the
power supply. Hold a parking light bulb so it is being energised by
the two brushes. Start to raise the voltage - the light will come on
faintly and slowly get brighter. As it reaches around 14 volts, the
light should suddenly go out. Lowering it back to around this voltage
should cause the light to come back on again. Now drop the light
bulb, as it has become quite hot! Please don't hurt yourself or your
tools - you should only be doing this if you have experience working
safely with electricity."
I found a different result, light would increase in brightness as
power supply input increased until an indicated around 12.5 V on
voltmeter, the light would go off and voltmeter would indicate 14.2
V. Mmm, well the reg seems to work, it is regulating but at 12 not
14. Ah well, lets see how it works in situ
Ok, everything put back together, contact grease, shiny connections,
everything. Started van up, no whine, good. Then I checked voltages
at alternator and at battery....
13.5 at alternator, 13.4 at battery (13.47/13.38 actual values). What
the heck?!
Then followed much connection cleaning and ground checking. I didn't
find any poor looking connections but i was convincing myself I was
on the right track. I even added an additional ground from engine to
body. None of that made any difference.
Today i was in workshop and I thought I would check the hand held
volt meter I had been using throughout this fandango, using my
variable power supply and a bench top plug-in phillips voltmeter.
Well it seems that the hand held voltmeter differed from the bench
top voltmeter by about 0.5 V.
I took the bench top out to the van and checked the alternator... 14
V at alternator, 13.9 V at battery. I need a third voltmeter to truly
convince myself, but I am suspecting the hand held meter is in error.
Still a 0.1 volt voltage drop, something that running a new wire will
help.
Morals of the story:
1. soldering in new brushes is easy and cheaper than new reg. Good to
do on your spare reg.
2. get a good voltmeter and check it once in a while. check it more
than once in a while if you have a crappy tire model like mine (it
seems to need fresh batteries to read well)
cheers
alistair
'86 syncro 7 passenger
'82 westy, diesel converted to gas in '94
http://www.members.shaw.ca/albell/
http://shufti.wordpress.com
