12V system down yet 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?

 

[Maitken1]

Have you checked the earth strap from the leisure batteries. Maybe that is loose where it connects onto the chassis. It sounds like an earth problem. There is obviously something not connected properly between the batteries and the control panel or just the earth to the chassis if that's what the control panel is connected to. Or from the battery to the control panel. When you switch the charger on it may also be connected through the control panel so it would light up the control panel. Just a suggestion!

 

[berni109]

From that reading the batteries are probably stuffed.
U are getting 12.8 from the charger attached to the batteries.

 

[Cush]

Morning Nick26 ,
did you take your multimeter reading before attaching hook up / ehu?

if you did then as above, earth strap, or the inline fuse. If not then the reading would be as a result of a charge going to them from ehu.

It“s quite normal for everything to work on ehu despite having duff batteries. A pic of your panel may help those with a more detailed knowledge of your van. Do you have solar?

good luck

 

[Pausim]

There should be a large fuse close to your leisure batteries. This fuse is the main connection between the batteries and the rest of the 12V system. The charger usually connects to the 12V system elsewhere and can work independently of the batteries. I suggest checking this fuse with your meter, don’t rely on a visual check.

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[Nick26]

Thanks for all your inputs. Breaking and remaking a 4 wire joiner between batteries and PSU has done the trick, at least for now. Thanks again.