It was actually the switch. The switch was shorted out internally and one
terminal was shorted to the exterior case of the switch and ultimately to
the panel.

Jim

"Dan Thomas" wrote in message
om...
"Jim Burns" wrote in message
...

It sounds as though you have corrosion or some other resistance in
the
circuit. I would check for a voltage drop across the circuit breaker
and
switch
while the circuit is under load.

Bingo.
voltage drops to about 0
played with it enough that the circuit breaker started popping
corroded terminal on the switch/lead to the circuit breaker

hooked a battery direct to the pitot heat terms and it works fine

will try a new switch & lead tomorrow

thanks all!

Jim

Bad breakers cost some folks a lot of money. We once replaced a
$600 strobe power supply because we got battery voltage at the strobe
power plug, but that was with the plug disconnected from the strobe.
The relatively high resistance of a bad breaker won't drop voltage
detectably with only a voltmeter drawing on it. Learned the hard way
that voltage drop measurements across suspect components are much more
informative.

Dan


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