Dometic RM2350 Fridge not cold enough

Question

Hi .I was wondering if you are able to give some advise please.Iwas looking thru your website and believe you are the people to helpwith my delima.I have a Dometic RM 2350 fitted to a van we havepurchased. It' is 4 years old & I have to run the fridge on max toget it cold. It was on for 4 days on this latest trip & tried it on240v for 1 day, 12v for 1 day & gas for 1 day and the temperature doesn/t seem to get any colder or warmer.The van is level in both directions.It is well ventilated thru the vents to the outside of the van.There is no smell of ammonia.There is no gas/gurgling noises from the unit.The seal on the fridge door is in good cond.would I be correct in saying the thermostat is not working correctly?Thankyou for your time on this matter. Cheers Steve Phillips.