Is it self defrosting? Much more complicated if so. I would hardwire the compressor bypassing any controls to see if it starts. There is always a wiring diagram somewhere on it or on the net. The non self defrosting freezer causes more freezer burn than self defrosting.

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Tony H
W111 280SE 3.5 Coupe
Manual transmission

Past cars:
Porsche 914 2.0
'64 Jaguar XKE Roadster
'57 Oval Window VW
'71 Toyota Hilux Pickup Truck-Dad bought new
'73 Toyota Celica GT