Motorhome starter battery draining

[Mullacrew]

Hi there. My parents have just bought a 1997 fiat ducato eldis motorhome.
When viewing the motorhome the main battery was connected to solar trickle charge unit. This had been disconnected by the owner on collection and the motorhome would not start. Motorhome was jump started. The owner assured us that all the batteries are quite new and he must have left a light on. Motorhome will not start since without a jump start.
I have noticed that the control panel is always lit up which is obviously drawing power from the main battery. obviously a wiring issue somewhere. Can anyone help.
I have disconnected the 12v invertor.
Even when leisure battery is disconnected the lights remain on.

 

[autorouter]

It looks like someone has their wires crossed. Is it possible the wires from the two batteries have been interchanged at the control panel. If the control panel is just a controller wired to a distribution/fuse box maybe they are miswired there. If for example they are labelled B1 and B2, somone could have mixed them up if they removed the controller for repair. Clearly something is seriously awry in the wiring.

 

[Mullacrew]

Thanks a million Autorouter.
I shall follow the lines and see. Yep. Definitely some mess up...
Cheers

 

[pappajohn]

When viewing the motorhome the main battery was connected to solar trickle charge unit

And for a reason.... The battery is knackered regardless of what the seller said.
Obviously he's not going to tell you it needs replacing.
As for the other issues....multimeter and investigation.