Question

Dear Tom. The Truma Ultraheat system in our Autotrail Dakota has failed, it was working fine it was switched off and later switched on nothing happened any ideas? P.S what is a PCB?

Answer

If the Ultraheat is not working the first thing to check is that there is power reaching the circuit board, i.e. check that no fuses have blown, and check that the wiring to the wallswitch is connected properly.
It is then necessary to check the continuity of the over temperature switch and the temperature sensor. For the overtemperature switch you need to check the continuity between the two black wires on the printed circuit board (PCB). This is situated at ground level behind the fire. If there is no continuity then replace the over temperature switch, our part 133316. If this is OK then check the continuity between the green and blue wires on the PCB. If there is no continuity then replace the temperature control sensor, our part 133317.
If both the over temperature switch and the temperature sensor are OK then the next stage is to replace the printed circuit board, our part 133335.