Question

I have a compass caravan fitted with a truma crystal filter and a submersible pump. When the taps are on the LED lights up on the ZIG unit to say pump running. the pump sometimes will run for about 20 seconds then stops, then will run no more. I have checked that there is 12volts at the pump connection (back of crystal filter unit) when taps are on. The pump works when connected to an independent supply. As soon as the pump is plugged in the 12 volts disappear. Any ideas would be gratefully received. Thank you.

Answer

This may indicate a bad electrical connection at one of the terminals in the system. If you have microswitches in the taps then try each tap in turn to see if same symptoms are evident from all taps. If only evident from one of the taps then you probably need to change the microswitch in that tap.
If you have a pressure switch in your water system than it could be a fault with the microswitch included in the pressure switch.