Test the switch for continuity
using a multitester.
Set the multitester to the ohms setting X1. Place a probe on each
terminal. The multitester should change from a reading of infinity
to zero when the probes touch the terminals. With the probes still
touching the terminals depress the switch, the reading should
change back to infinity. If it does not pass both of these tests,
If there are four terminals, touch the probe
to one terminal and then test each of the other three terminals
with the other probe one at a time. Touching one of the three
terminals should cause the multitester reading to change from
infinity to zero. Those two terminals are a pair. Depress the
switch with the probes still touching the terminals and the reading
should change back to infinity. Now test the other two terminals.
If either pair of terminals fails the continuity test, the switch
should be replaced.