Paul, and others,
This must be a prime example of no 2 coaches being built the same.
The receptacle in the rear engine bay is for the block heater and on my coach there is a switch on the side panel among all the other switches. Plus there is a dedicated 15 amp breaker in the electrical panel above the driver window.
Unless it’s cold and I plan to use the block heater, I generally leave the breaker off as one time we returned and I was trying to determine what was drawing power - our little dog had switched the block heater on; not really needed when it was 75 outside!
Jeff