I posted a follow up post in the techo section but then thought it would be worth also posting in the general section as a lot of vans have Suburban water heaters, my on off rocker switch which is accessible from outside the van had frozen in the on position which created a problem when there was no water in the tank and I wanted to charge my batteries, I have discovered that there is a power point behind the row of draws in my Heritage van which has a front kitchen.

I think any van that has a suburban 240 volt water heater will have a lead running from the heater to a power point and even having to remove the top draw to reach the power point is much easier than getting access to the rocker switch even if it does work as they are in a ridiculous place on the heater where you need to be a finger contortionist to get to them.

Hope this helps someone sometime

Yes ours has an inside switch and we always  use this switch when on 240v.

Yes ours in the Jayco Sterling is under the seat easy to get to. I have to turn it off when we are free camping as I turn my van over to my Inverter and put the fridge and Suburban onto gas. If leave it turned on at power point it runs off the inverter, drains the battery in 5 or 6 hours. With gas I just turn it on 1/2 hour before needing water as in shower or washing up.