When I happened to select the home screen of the main Firefly display today, my chassis battery was reading zero. I had previously disconnected and reconnected the ground by the accelerator pedal while installing the Blue Sea BIM.
The voltage at the 2 amp fuse on the coach side of the BIM read correctly. I pulled the cover of the main Firefly board and the connector for the coach battery and generator hour meter was in place and secure. I pulled that connector and the correct voltage for the chassis battery was there. I plugged the cable back in and the main Firefly display showed the correct voltage. For whatever reason, the Firefly did not detect the chassis battery coming back on line, but hot plugging it made it work properly.
The coach battery voltage on my main Filefly display reads about 0.4 volts low, compared to the chassis side and the Magnum display just above. My meter confirms that the Magnum display is correct. The BIM is actively connecting the two batteries and they should read the same. I think I have a defective Firefly board. The low reading can be a bit scary when not connected to outside power.
John W. Irwin
2018 Interstate GT, "Sabre-Dog V"