on the reduction gear starters the most common wear item are the contacts
in the solenoid part  later  mark d

In a message dated 8/12/2011 1:02:16 P.M. Eastern Daylight Time,
poppie.jagersand@YAHOO.CA writes:

After  the details, here are some global observations:

The most common problem  I've seen with the vanagon diesel starters is that
the nose cone bearing  wears. In the extreme this will make the starter
gear disengage when  cranking.

The second most common problem is slow cranking.
Brushes  can be too worn, commutator pitted, or individual brush holders
mis-aligned.  (I've also seen the holders come loose). All of these problems
are easy to  identify.

A more nefarious problem is when cranking is slow despite  everything
looking right. Then I'm thinking there could be a current path  problem. The
return current to ground goes from the brush holder through the  two dinky
screws to the rear housing and rear bushing grease cap., then the  housing is
three separate parts until it is finally screwed onto the bell  housing.

There are two parallel current paths, each though one of the  small rear
screws. If contact is bad (grease on screw, brush holder) on one,  the motor
will only give half torque. Anyone else things this is a reasonable  theory?

Martin

----- Original Message -----
From:  Poppie Jagersand <poppie.jagersand@YAHOO.CA>
To:  vanagon@GERRY.VANAGON.COM
Cc:
Sent: Friday, August 12, 2011 10:38:02  AM
Subject: Re: Starter motor do-it-yourself rebuild

Here are some  more starter observations. I pulled apart and compared the
two different types  currently available for our Diesel vanagon. As Neil,
Bryan and others have  noticed, when you get a rebuild you may end up getting
the smaller swapped for  the larger and vice versa.

member NYSwanderer put some photos on the  web, and wondered what the
differences between them  are.
http://groups.yahoo.com/group/Diesel-Vanagon/photos/album/1381430081/pic/449
269473/view?picmode=&mode=tn&order=ordinal&start=1&count=20&dir=asc

I  took them apart and here is my side by side comparison:

The smaller is  a gear reduction starter using a planetary gear and has a
permanent magnet  motor. The larger one is a direct drive  motor with
windings in both  stator and rotor connected in series. Both AFAIK meet spec.

I have a  torque/power graph for the smaller one from a rebuilder.
If someone got a  graph for the bigger it would be interesting to compare.
Please scan and email  me and I'll post both.

In theory the larger starter could have both a  higher peak torque and a
higher max rpm. That comes from the fact that both  rotor and stator windings
are connected in series. When stalled or at very low  rpm, the high current
will increase the magnetic field in both the stator and  rotor. By contrast,
the permanent magnet motor has a fixed magnetic field from  the ferrite
magnets (that may even go down if the starter gets hot).

For the series motor as the rpm increases the magnetic field weakens.  This
field weakening yields a lower back EMF in the windings, and thus allows
for a higher RPM.

These are differences you learn in a motor text  book. The gear reduction
and design of the smaller starter may very well make  up for them. That's why
it would be interesting to compare test  graphs.

Mechanical differences:
I don't think many internal parts  interchange. I tried to use the studs
from one on the other, but threads were  different. Brushes and brush holders
are different.

At best there  seems to be some chance that solenoids and end bushings may
be the same, but I  need to check. Or someone with Bosch data tables can
find out.

The  smaller one have very brittle ferrite magnets. Don;t drop your tools
or they  can/will shatter. The bigger one has robust copper windings in the
stator.

Another note on the smaller starter: nyswanderer remarked that  he saw no
Bosch markings on his, so it must be an aftermarket. I however got a  smaller
starter that a friend had brought from Germany. That is an original  Bosch
with markings. I got another one with no markings.

Martin (and  '82 Westy 1.9TD "Poppie")

----- Original Message -----
From:  Martin Jagersand <jag@CS.UALBERTA.CA>
To:  vanagon@GERRY.VANAGON.COM
Cc:
Sent: Saturday, August 18, 2007 9:12:00  PM
Subject: Starter motor do-it-yourself rebuild

I just rebuilt the  starter for my '82 Diesel Westy. Last time I did it was
in '99, I think, so  the previous rebuild lasted about 8 years.

Bosch rebuilt starters can  run near $200 nowdays, but rebuilding it
yourself
is not hard. Here are  some tips:
(Edit 2011: I was quoted from 200 to $400 for a Bosch rebuilt,  $100 to 300
for others)

First check that the problem is really the  starter. Measure the voltage
over
the starter itself while cranking, ie  from the positive iput terminal on
the
starter to the starter housing. If  it's 8-10V and the starter still is
cranking slowly the starter is most  likely bad. If battery voltage is ok
but
voltage at starter is low check  voltage drop in the positive and negative
circuit. When I measured I had  .2V drop in the neg circuit and .9V in the
positive. Of the .9V .7V was  over the solenoid and .2V in ther actual
cable.

If it is not starting  at all, no noise, no click, despite having 12V at
both
starter and  solenoid, check connections to the solenoid, and then between
solenoid and  starter. This time I found that the metal tab running from the
outside of  the soloid terminal and connecting the solenoid winding was
sheared off. I  soldered on a flat piece of copper (from a water pipe ground
strap) to fix  it.

So you determined that its the starter. All Bosch starters, gas or  diesel
have the same basic design, but the sizes and housings are different
between
different models. Get the right parts!

Wear parts are  basically:

1/ Bushings: 3 total. One in each end, and one in the  middle. The latter I
don't think carries much load. Cost: about $1 each  from the Bosch
distributor.

2/ Brushes: 4 in total. You can buy  either a brush assembly for $45 with
the
4 brushes already mounted, or 4  loose brushes for about $15 total. If you
get loose brushes get ones with  small u-shaped metal ends welded to the
copper braid. They are much easier  to solder to your brushholder.

The above is Bosch prices VW dealer  prices are about twice as much.

Rebuild procedure:

1. Unscrew  the two small screws on the commutator housing (back) this
releases the  brush holder.

2. Unbolt the two studs in the back. Now the commutator  end comes off after
removing a circlip on the end of the shaft, and the  rotor is loose, but
don't pull it off yet.

3. Loosen the 3 screws  holding the solenoid to the front housing.

4. Between the solenoid and  the starter motor is a small rubber piece. See
if you can loosen it.  Carefully wiggle and separate the front housing.

5. Solenoid and  starter can be separated at the solenoid end. Take off the
solenoid. (To  prevent binding wipe off any dirt or corrosion on the
solenoid
plunger  before reassembly)

6. Determine shape of bushings. The gear end bushing  is in the bellhousing
on starters for transverse engine models, and in the  front housing on
longitudinal engines. Replace front and rear bushings if  worn.

7. To get at the middle bushing remove the ring and c-clip in  front of the
gear. Slide off gear assembly. Take out plate holding middle  bushing.
Replace if worn.

8. Check brushes. New brushes have about  8mm between the tip and the copper
braid. I'd replace them if they are more  than half worn. Also if the
bushings were really bad the starter shaft has  been riding out of center,
and the brushes have been wearing irregularly  and need replacement.

9. Snip off the braided copper holding the old  brushes. Don't lose the
springs! File off any remains from the brush  holder. Solder on new brushes.
Make sure they are soldered well. Each brush  will pass 100's of amps at
startup!

10. Inspect the commutator. If  pitted (from arcing) sand/file down until
clean and smooth
copper. If out  of round use a lathe.

11. Assemble the parts. Grease bushings and gears  lightly. You don't want
grease on the commutator or too much so that it can  spatter on the clutch.

--
Martin Jagersand
University of  Alberta
http://www.cs.ualberta.ca/~jag/