We have a problem with the Truma water heater in our Coachman Amara 520/4 year 2000. It works great on the electric side but when trying it with the gas we are having no joy. We bought the van in February this year and it has never worked with the gas. When putting the switch to on after a few seconds there is a click and then a red light comes on the panel. Can anyone offer any help on what could be the problem please.