Mark Hansen wrote:
We have a plane in our club (1978-ish C172N) that has a problem
with the pilot's push to talk switch. It is mounted on the yoke
handle (as if from the factory, not like an after market).

When you press it gently, it works fine. If you press it too hard,
the radio continues to send the carrier, but voice is no longer sent.

Not recognizing what the problem was, after the first complaint from
ATC, I pressed harder on the switch - making the problem occur 100%
of the time. To work around this, I used the built-in hand mike for
the rest of the flight.

It was only after I got back on the ground and began diagnosing the
problem did I remember a notice from the club admin to all members
that this is just how these switches work, and that you must not
press on the switch too hard. Of course, that's just not Human
Nature ;-) If the switch doesn't work when you press it, you press
it harder.

Is this really how "these switches" work, or is the switch defective?

Mark,
Sounds like you have a short to ground in the mic line. Have the switch
pull and see if it is contacting anything underneath.

Michelle