Dometic RM7651L cooling excessively

[Lie-in-King]

I have the above fridge/ freezer model installed in a 2005 Bailey Lousiana van. It's the curved door version of the appliance. It worked fine last year, but this season the fridge is lowering the temperature to minus 4.6 degrees C even on the lowest setting on the fascia dial. Last season the same dial maintained a temperature of about 3 degrees C at the half way point on the dial. As a result, this year everything's freezing solid within the fridge compartment. The freezer section is currently around -18 degrees C on the lowest section.
I think this points to an issue with the thermostat but I'm having a devil of a job finding a replacement one. Most sellers say that what they sell should be compatible and should work but they don't commit themselves further. I'd be grateful I'd someone could point me in the direction of a thermostat that will fit without the risk of having to return it to the seller. Can I also ask about how difficult these thermostats are to fit? Is it simply a case of removing the temperature control knob and going from there? I take it the thermostat fits behind the knob with the wire feeding down into the fridge section?
Thank you.

 

[Jcloughie]

You seem to have made a good assessment of your issue, I am surprised a caravan fridge can get that low.

I can’t help directly. But failing getting the correct thermostat. You can buy one of these quite cheaply, and if you search you will get on in a box.

Mount it outside of the fridge, with the sensor fed through to the freezer. Adjust to the temp you want from the freezer and forget it.

The relay could then turn the fridge power on and off.

John