Norcool CU450 thermostat not working

[cyberkul]

Hi!
Got a used unit for my walk in cooler. The unit cools, but it doesn`t stop, and the temperature knob doesn`t seem to do anything. Isn`t it supposed to stop the compressor when the set temperature is reached? The defrost timer seems to be broken, but if I turn it manually the compressor stops, and the defrost light turns on. I have some used parts, and I replaced the thermostat, (the item with the purple wire..) but no change.
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The purple wire goes to another item with the purple wire ant two more wires at the bottom. Is this a solenoid? It is the disc shaped item in the middle of the picture. The wires doesn`t show. What is the function of this item? Can it simply be unscrewed and replaced?

IMG_3391.jpg

Thanks for any help!

[cyberkul]

It seems that the unit I replaced doesn`t have the disc shaped item. Instead it has a start capasitor. It is probably a few years newer than the unit I just installed. Both are Norcool CU-450. The reason for the replacement is a bit weak cooling capacity, and a cracked defrost "reservoir". It could be that it will help to clean the condenser, as it is probably covered with a layer of fat from cooking. I`ll try to test the therrmostats, and if necessary take the thermostat from the replaced unit.