As with our last van we found it very difficult to control the temperature evenly throughout the van. The temperature sensor on truma heaters is built into the temperature control knob which may not be located in the best position.
You can buy an additional remote temperature sensor on a long lead that plugs into the back of the heater which then over rides the sensor in the control knob.
There are many locations suggested for the positioning of the remote sensor I chose a position at the bottom of the heater to monitor the temperature of the air entering the heater which seemed to work well.
A fiddly job that needs some patience as finding that plug at the back of the heater is like looking for a needle in a haystack – although I think there is a YouTube video to help
My Motorhome Mods .Online 