"Peter Dohm" wrote in message
.. .
..

Additional possibilities include shorts behind the instrument panel, or
even
in the ignition switch or switches--since a magneto is dissabled (turned
off) by shorting the P-lead toground.

In addition to the magnetos; common failure modes include mixture and
throttle control cables and fittings.

Like Dylan, I have found the automotive ECMs to be far more reliable in
service than the old breaker ignition systems. I have had a defective
throttle positioner which resulted in a higher than normal idle speed, and
a
rough running engine due to a defective spark plug, but nothing that
disabled the engines. So, personal feelings aside (which I admit is
another
issue), the ECMs and FADECs seem to have better long term reliability than
the mechanical/manual systems they replace--and they may far fewer
mistakes
than I do.


But that's a completely different kettle of fish. I was wondering what cause
the dual mag failure on a 172.