@karenbobiv
I doubt it's related to the MySensors communication. Are you using a Dallas temp sensor? Could you check that the is actually connected to the dallas sensor by using isConnected().
When googling your problem I found a few hits on -196.6 which is the error code (DEVICE_DISCONNECTED) converted to Fahrenheit.
Start debug mode (Config.h) to see what the sensor actually sends.
the problem is "if (switch.state == 'On') then" that not works, write:
if (switch.active) then
or
if (switch.inActive) then
Device attributes and methods for all devices
