1. Make sure the slider (if so equipped)
on top of the switch is set to
regular operation instead of 2-train
operation.
2. Turn the switch over. On the
bottom you will see a metal plate with 3
small screws. Remove the screws
and the plate. You will see two metal
contact plates with a wiper that
slides back and forth when the switch is
thrown. Clean the contacts and wiper
with electronic tuner cleaner and make
sure the two metal points on the
wiper make good contact with the plates.
If necessary, GENTLY bend the points
upward to reach the contacts. Now
re-assemble and try the switch.
If you are lucky you can quit now.
3. If it still doesn't work and
if you can find a volt-ohmmeter, use the
ohmmeter to check the continuity
through the contacts and rails to determine
where the open point in the circuit
is. If you don't have a VOM, you could
try the same thing with a battery,
a flashlight bulb, and a couple of
lengths of wire.
4. Only in desperation if nothing
else works, I would consider cleaning the
wiper points and contact plates
with extremely fine (600) wet-or-dry
sandpaper. But you risk wrecking
the points. I would definitely do step #3
to determine where the problem is
first.
Good luck.