What's inside, What not to do, How to fix it.
If you remove it and then plug it in and turn on the bike,
it launches the small parts to the right. It's not the end of
the world, though...
Left; all the parts. Right, view into the stepper.
DON'T DO THIS!
The stepper 'fix' procedure is at the bottom of the
page, and isn't terribly involved. This was my journey
of discovery that totally destroyed my stepper, but
revealed how to save yours.
The case is held together by these little rivet things.
After grinding off the rivets and driving them into the
case, this is what you find: it's a little stepper motor with
no user serviceable components...
The tiny wires are motor winding wires. Not stranded wire
they break with ridiculous ease. Another bad thing.
Left, good view of the tiny wires. Right, the posts they are
soldered to. I was able to resolder the one that broke, but
the length is critical. The shortest one breaks, of course, and
then it no longer reaches after you fix it.
What appears to be a screw on the stepper valve is: it's a
lead screw. The small grey part in the stepper motor acts
like a nut on the lead screw thread. The motor spins it and
the shaft is extended or retracted. The shaft can't turn due
to the fit with the white plastic collar visible in the first 2 pix.
If you have already launched the little parts, but have not yet
torn the thing apart destroying it completely, here is my advice;
Put the spring on, then the collar. Push the collar down so you can
see the white plastic part the plunger goes into. Align the lead screw
so that the flanges and slots fit together and PUSH. Wiggle it a bit
to get things going if you have to. You should be able to get the lead
screw to spin the nut and reinsert itself. Now put it back in the bike
and turn on the power. The stepper will go out a good bit, then back
in a short way. Turn the bike off, then turn the bike back on. The
Stepper can take 3 cycles to get to the fully extended position. When
it's back all the way out, you should be back in business! Cool!!
The stepper is a simple unit with no internal homing system. In order
to find home, the computer steps it out a little further than it ever goes
in normal use. When the plunger bottoms in the housing, the stepper
motor tries to keep moving it out, but just slips back electrically. The
plunger is pressed against the stop, fully closed. Now the computer knows
where the stepper is, and counts steps backwards from there to go to the
calculated position. The problem is that when the stepper is not in the
housing, the lead screw runs out of length and the spring launches everything.
Questions or comments?