Water pump and inlet

Recently acquired a 4 year old Stratford. Water pump worked but with different sounds on each use. When filling via Whale systems, both mains and container with external pump, both systems shut off automatically, when the tank was full, due to a hidden valve. This valve also prevented input if the internal electrics were not switched on. After filling on the third day of our trip the pump ceased to work at all. Upon return it became apparent that the shut off valve did not work either and tank filling can cause overflow. Could these two phenomena be Connected? Is there a circuit diagram? Incidentally an unnoticed overflow caused the door open alarm to sound until excess water drained and  everything dried out!! About 10 miles! Also a Shurflo pump temporarily plumbed in place of the existing pressure switch works beautifully but not installed - yet. I am currently making a large spanner to twist off the tank bottom inspection panel. Any advice would be greatly appreciated.

The Shurflo was lovely! About 12 litres per shower. Made the spanner and replaced the broken Whale pump without having to raise the van in any way although it doesn't do to be claustrophobic. Now to replace the broken 'full sensor'. It certainly does not look like a float switch.

As you've probably seen in numerous other threads here, the Shurflo pumps are so much better than the original fitted ones that it's a good idea to stick with it if you can - my own experience of them is that they are incredibly reliable, while the impeller pumps are not.

The circuit diagram in the Owner's Manual is as good as you will get, sadly - which means that you get very little detail at all about such things as water level sensors. Typically (if you have a power control system by Sargent) these are just contacts and there are no moving parts. They tend to corrode, or get covered in crud, or water tracks down the connections on the outside of the tank. As you can see from lots of similar threads here, there doesn't seem to be a way to get them to work reliably long-term, so it may be a good idea to give up on that now and accept that you will have to use other methods to infer that it is full!

Thanks so much for the insight! I am looking longingly at the natty little float switches in the CAK Tanks catalogue. Now, if this could be married to the Sargent requirement of some resonant circuit or whatever.... Back to AS first!