Heating thermostat placement

Hi all,

I have a 2004 Burstner van. The living space heater works really well and heats the van to a lovely warm temperature, even in sub zero conditions. The problem is that it doesn’t want to switch on. The temperature sensor is placed on the control panel above the habitation door, which is next to wardrobe which houses the hot water tank. Heat from the warm wardrobe is trapped above the door where the temperature sensor lives, and so even with the heating cranked all the way up, it doesn’t kick in because it’s 27’C where the sensor is. A frozen bag of peas pressed against the sensor for a few minutes does the trick for a half hour, but then it goes off and stays off again. With the heating set to max. The habitation area would need to drop to around 16’C before it switches on (unless you use the frozen peas trick). I know that with more modern controls you can calibrate the system to compensate for this issue, but mine pre-dates this facility. I’m wondering if anyone has fixed such an issue and how it was done. All input is appreciated.