Fridge thermostat replacement

[jha]

My Beneteau Oceanis 423 has a 12v frigoboat icebox aircooled system and a CLD system with a large cold plate that works off the engine or shorepower. On the latter the Johnson thermostat (mechanical) will cut off the compressor when it reaches it's cold setting but will not turn it back on when the temperature rises. By turning the fridge off and back on again it starts working.
The thermostat is 12 yrs old I guess, as is the system. I believe the temperature differential has now widened with age. Any thoughts?
If this is the case I need to fit a new one. Electrically no problem but there is no easy access to mouse the new temperature probe into the fridge. The thermostat sits in a cupboard above the fridge, which seems fixed , having removed all screws.Clearly I need to make some opening in this cupboard floor to gain access and if so any advice?
Many thanks.

[jha]

Having tried a new thermostat that is NOT the problem. Does anyone have an old manual or info re CLD fridge or power management systems. On the management panel when the fridge is working the green AC power light flashes, when it reaches the set temperature the green light now stays on and the low battery and high temperature lights now all remain on. After a while the fridge will restart ie thermostat has reset but after the next time the green light goes out and the low battery and high temperature red lights flash and the fridge wont restart automatically again unless you turn off and restart.
It is a CLD OND 800 Power Center.