If the pump has been working fine then suddenly encounters a problem then a low voltage battery or a battery failing to hold a charge will cause a pump the run continuously so I would check the battery voltage with a voltmeter.
If it is low then check the battery charger (if you are on electric hook up) as well as that could be defective.
If on mains water,different water pressures will cause the pump to run on,if it runs ok on one site but not another,then all you need to do is alter the setting on your pressure switch,truma(if that's what yours is,) have an instruction leaflet explaining how to do it,you can download and print off their website,I had a similar thing with mine,scratched my head a bit and found no water in the aquaroll
I have the Truma fit and have found quite often the inlet hose slackens in the trigger housing allowing air to get in and causing the pump to run on. Pushing the hose into the trigger cures the problem.