HUW! Re: Alternator Electrical noise and Belts?

[Huw Powell]

Going public with Q & A for better feedback, etc...

>   Can you forward me the info I need to replace the brushes in
> my ALT.  I have to rev the car to about 2,500 RPM before it will
> kick in then its fine unless the idle dies below about 800-900
> rpm.  HOwever at Idle its only putting out aboutu 12.5v.  Rev to
> 1200 and I get 13.4v.

Remove voltage regulator/brush assembly.

Drill out rusted grounding mounting bolt and re-tap hole.  Obtain
stainless replacements.

Measure brushes, about 1 cm sticking out is the wear limit, I think.

Examine to see if they will be easy to unsolder from the backside.  The
braided "tinsel" lead is what stops them from popping out, a spring
around it pushes them against the commutator (that's what the rotating
contacts are called, I think)

Obtain replacement brushes (with springs and tinsel).  Maybe this was
step one.  You can get them from a dealer, or wander into a hardware
store with an old brush.  Buy a pair that are identical or slightly
thicker - I got some 1/4" x 1/4" ones and filed them down.

Remove old brushes be desoldering, clean up solder hole.

Place new brush in place, hold to appropriate depth (guess) and secure
tinsel with finger to trap it.  Resolder carefully, let cool without
letting go of tinsel.  Repeat for other brush.

Carefully replace assembly on back of alternator.

Test.

>   Anyhow, is that the symptom of bad brushes?

In my experience, the symptom has been a problem with charging overall,
ie, maybe only charging at very low rpms, or losing it all over the
range randomly.  until it won't charge at all.

The *actual* symptom of worn brushes is that they are too short, you
simply measure them.

While they are out, clean and maybe burnish the commutator a bit.  I
suspect you may have commutator or other issues.

But there are test procedures to isolate all functions of an alternator,
digging them out and running through them is the only way to know where
the fault lies.

Good luck and have fun!

--
Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/