(ET) troubleshooting - dead tractor

[David C Robie <mycroftxx1 juno com>]

Lotta things can cause this. But some are more common than others.  This
one's common.
This was first mow with tractor after using her all winter to blow snow.

Tractor GE E16,  a 15 without the big PC board, only a little field
resistor board.  (a 15 can be convrted to a 16 if the big board is wiped
out or missing but you gotta know your electricity to do it, 16 schematic
is NOT in the big green GE manual. (they all shoulda been 16's that big
15 board is ridiculous, unnecessary.  Do I hear an engineering type scoff
at this statement?  Let's dialog, explore the subject.)

* Symptom:  Died at shift to reverse after 15 minute mow.  Sealing
contact relay clicks. no klunk from big armature resistor relays or hi
current F/R relays.  Lift OK.  DID NOT use brake to stop.  Seat switch
permanently jumpered out on this tractor.  No motor heat.  External motor
thermostat. (didn't bother to check it, uncommon failure)
Deck lights and winch OK.  Obvious first guess, no hi current ckt derived
36 available to big relay coils 

 * Begin: 1st test,  mech shift in neutral. test by pulling belt be sure
it is in neutral,  check  controller fuse and it's push on terms at fuse
box.  Batt switch on,  brake off,  seat switch satisfied, key on (click!)
  Jumper em. attempt restart.
(this place is famous for stranded wire broken inside insulation at push
ons so pull the wires to check that)

*  2nd test.  jumper right armature resistor at front of tractor, then
left one to center terminal on resistor assy attempting restart each time
Voila !  Right resistor jumpered, motor ran. Reason;  36V relay power is
derived AFTER these resistors. An open resistor denies power to all 36V
coils except the sealing contact relay.
    What had happened;  With the years, the brass bolts washers holding
the nichrome element had lost tension, corrosion happened through
excessive heat at that point, and contact was finally lost.
    Solution;  Remove the 3 brass bolts one at a time and clean all
contacting surfaces.at the resistor element. A small stiff wire brush and
a fine file (for the inner bolt head and brass washers) is all that's
necessary here.

Have seen a burned up element here at a bolt head.  My solution is a
piece of flat 1/8" or so brass as wide as the nichrome  with a 1/4"
clearance hole at the center which will make full contact at a different
point than the original brass washer did.

When tightening;  Remember you are tightening up on a ceramic tube spacer
so don't use Godzilla tactics with the wrench.  It must be better than
snug.  I use a short 7/16 open end 'tight' here is not sufficient to
break the tube. A sloppy connection here you will have the same trouble
again, a hot bolt and corrosion and a deadster.  You can see discolored
brass washer and bolt head usually but not always.

If these tests don't get your tractor back, look for corroded conns etc
in the same 36V hi current  end first.  This has been at the other terms
on the armature resistor relays themselves. 

BTW: You guys that haven't discovered yet that Gibbs is the absolute best
rusty bolt solution are working too hard on these things.  This is a shop
that works on a lot of various 'old rusty stuff' and upon discovering the
difference between it and a lot of other brands tried, bought a case. 
WD40 has it's many uses, but is at the bottom of the list as to freeing
up rusty bolts, frozen shafts and bearings, quieting squeaky auto springs
etc.

Dave
Weymouth MA