We have a problem with our kitchen hot water tap, when we turn it on we get a good flow for about 30 seconds then nothing but a dribble comes out. The cold water is fine and so is the hot water in the bathroom. Any ideas what could be wrong?
Could be the microswitch in the tap. When water is heated in the boiler it builds up pressure, thus when you open a hot tap it will flow for a while irrespective of the pump running.
Try checking it before you start heating the water, that will prove at least that one theory. :)
It would be helpful if you could give some details of your van to assess the type of water system you're likely to have. That said though, Crypto's theory could be right regarding a failed micro-switch, if this is an older van that uses a switched water system.
One way to check is to turn on the washroom hot tap, then turn on the kitchen hot tap. If water flows from the kitchen while the washroom tap is running, this would indicate a failure of the switch in the kitchen tap, as the demand for water is being made by the (good) washroom tap.