The 12v charger/controller and the control panel has been sent off for repair.
The 12v controller controls the battery charging (from mains and engine), leisure battery supply, engine battery. the control panel shows the battery conditions, water levels, temperature, etc.
When we purchased the motorhome we knew parts of the control did not work, but nothing that stopped us using the motorhome.
I removed the control panel and there was nothing obvious wrong. I contacted the repair company who gave an estimate for repair. I also happened to ask them about connecting a solar panel to the controller. They said they would need to see the controller to assess the wiring and see if a solar panel can be connected.
This prompted me to remove the controller and take the top off. This revealed three burned out diodes and a burn mark on the circuit board. Hopefully this means the control panel is OK and the fault is only with the controller.
Fingers crossed the repair bill will be low and we will get them both back in the next week or so.
Will update with more news when I have some.