12V system down but batteries are fully charged

[Nick26]

My motorhome control panel shows a voltage of around 4V and the whole 12V circuit is dead yet both leisure batteries show 12.8V on a multimeter test. When I connect a 240V supply to the Power Supply Unit and switch the charger on the 12V circuit livens up and everything becomes fully operational. Can anyone offer advice/suggestions?

 

[Richard n Ann]

Sounds like a bad connection, maybe a fuse holder gone bad? I'd trace the wires off the battery and look for signs of heat on all the connectors and take voltage readings.

 

[Richard n Ann]

 

[berni109]

Triplicate post

 

[TerryL]

Bad earth connection