Thanks Dave,
It was the fan, it was only spinning at 170rpm, I cleaned the bearings and lubricated them now it’s spinning at 950rpm.
Now the temperature difference between the thermostat sensor and the shelf is about 8°c and the thermostat is not constantly clicking on and off.
Is 950rpm the expected full speed or should it run faster as I read somewhere it should run at about 1200rpm?
Thanks
Jon