For what its worth, I also had an intermittant transponder, and finally
concluded that it was due to the coax cable getting damaged by the heat in
the heater duct.

In my Warrior, the coax routes down through the heater ductwork to the belly
of the plane. Every winter, I would experience transponder trouble. I
finally insulated the antenna wire, and now there are no more problems.

"Bob" wrote in message
...
Is it possible that some oil on the transponder antenna would cause it
to transmit intermittently?

I would have wiped it clean and tried it out but it's 5 OVC today....

Thanx