My new (to me) van has an odd problem with the water - when I turn on the cold tap in the kitchen I can here the microswitch click on and a little bit of gurgling but no water comes out. If I then turn on the hot tap it works perfectly and while it's working the cold tap springs into life too if it's still open. The taps in the bathroom both behave themselves, it's just the kitchen cold tap that only works when the hot tap is also open.
It uses a submersible pump off the leisure battery if that makes a difference.
Def the microswitch, & depending on the system, can be replaced - we had the same issue - actually, the wires were loose, so check that before any major re-wiring job - wires checked & replaced & all OK xx
------------- Bringing up baby to be a seasoned caravanner - we bought one to holiday cheaply - working well so far - & caravanners are lovely - helped us on our virgin voyage & our awning!!!
I had a similar problem. The kitchen taps and the bathroom hot tap would only work if the bathroom cold tap was on. When I had it serviced the microswitches were just cleaned to see if that did the trick and it did, so worth a try before you have them replaced.