The pitot heat has failed on our Aztec. No heat, not even warm, no amperage
draw. Circuit breaker, switch, leads, and ground all check ok.

Now here's the strange part. We get correct voltage across the leads and we
get continuity across the terminals on the tube. No continuity from the
terminals to the tube itself, so I don't think the element is shorted out
against the tube.

If there is continuity across the terminals, one would think that the
element is intact. If it's getting adequate voltage, why isn't it heating?

The only explanation I can come up with is that the leads are shorted out
inside the tube before they get to the element. However, it doesn't pop the
circuit breaker.

Any other ideas?? Can these old style tubes be repaired? Ours is similar
to an AN5812-12 but we have rubber hoses connected to the airspeed and pitot
lines rather than 1/4" fittings. The AN5812's seem to run about $1000!

Thanks
Jim



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.