It is true that the normal heaters are heated with reduced voltage on the ground and full 115v in the air. The exception is....... you guessed it. The TAT probe.
From the MM.
'The system provides dual level pitot-static probes and temperature probe
heating through air/ground logic circuits in the E11 landing gear logic
shelf. When on the ground, the system provides reduced voltage to the
pitot static probes and removal of voltage from the temperature probe,
thus prolonging probe element life.'
This doesn't answer the original question though!