I'm not sure anyone was following this, but just in case here is an answer from Maxxair about the circuit boards.
The “B” model pcb had a range of 10.8-13.6vdc the newer “C” model has a working range of 13.3-15vdc. This was in response to the coach manufacturer’s use of lithium batteries and solar chargers. Both of them can produce higher volts. Any voltage outside of that range is going to set of a 30 second alarm and a flashing green LED warning you that there is a voltage present that the pcb does not like. Over time that voltage will damage the pcb.