we have a 2009 stirling outback with a solar panel. In the cupboard above the rangehood there is battery switch with a fuse. Above the switch is marked 240v with 12v written under the switch. The Jayco manual does not explain. The lights and water pump work regardless of the position of the switch  - even when its off and we are not connected to power. Hoping another Stirling owner may have the answer as to what its for and how to use it.

Have you tried a Jayco dealer or maybe Jayco themselves.

In my Conquest there is a switch that turns the battery charger  circuit off. If this switch is in the off position there is no charge to your batteries from either the alternator when motoring or 240v when plugged in.

When I purchased my Westport in 1999, the dealer suggested that I remove the in line fuse in the battery output/charge lead to prevent the gradual discharge of the battery when in 'storage'.

I put a switch in the lead instead & labled it 'battery'.  Did the same with the water pump lead as a backup to the anti-backflow valve to prevent it pumping my tank dry when traveling.  Put a manual stop valve (edit) in the water line as a later mod as well.

Maybe this is the function of the switch in question.

Note that in my case a charge lead from the Anderson plug/socket is not effected by this switch, so that charge from the vehicle via the Andersen plug is 'on' when driving irrespective of the switch.