Date: Thu, 28 Jan 2010 18:22:33 -0600
Reply-To: John Rodgers <inua@CHARTER.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: John Rodgers <inua@CHARTER.NET>
Subject: Re: alternators, voltages, rebuild, idiocracy
In-Reply-To: <2505CE71-CEBE-4EF3-833F-7C9B898F480D@shaw.ca>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Why buy just brushes for $13 when the entire brush pak including the
rectifiers can be had for $13.95??
John Rodgers
Clayartist and Moldmaker
88'GL VW Bus Driver
Chelsea, AL
Http://www.moldhaus.com
Alistair Bell wrote:
> 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
>
>
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