Westinghouse Upside down Fridge Freezer - Compressor always running?

[ol' boy]

Model: Westinghouse RB271K-R

Ok, this i thought was going to be a easy fix.

Picked up a Westinghouse Upside Down Fridge/Freezer for Free, as previous owners said it worked fine, it just froze their veges.
I'm just using it for a Beer fridge in the workshop, so i didnt mind.

Got it home and turned it on, compressor runs fine, fridge got cold
Put drinks in, all seemed fine for the first week
Then noticed the fridge was always running (the compressor)
Turned it right back to 1 and heard a click, compressor stopped.
Next day, it is constantly running again, drinks are frozen etc

To me, it was just a Thermostat problem
Ordered a replacement, installed it yesterday... Bugger me, it is still running the compressor all the time!
Fridge cabinet temp was minus 2.

Fridge is a very simple construction, no fans at all, has an Evaporator in the Fridge cabinet with Thermostat probe bolted to it
Has a Evaporator in the Freezer cabinet with no thermostat or controls

So it looks like the Fridge Evaporator plate with connected Thermostat does all the Temp Controlling of the fridge/freezer.

Fridge Cabinet showing Evaporator, Thermostat probe is sandwiched to plate under plastic cover (bottom left)



As a Sparky, i'm not the worlds best Fridgy.....
Is there anything else to look for ?
Surely it couldn't be a gas problem?

This is the Thermostat i used as a replacement, which is doing exactly as the last one did