"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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