Hotpoint FF187EPL Thermal fuse?

Hi, About a month back, I went out to this fridge freezer after a local numpty ripped out the neutral cable from the local sub station – blowing half the neighbourhoods electricals. This fridge freezer needed a new control pcb (located at the top) so I ordered it along with a low end adaptor and smart card. Fitted the pcb and dropped the software onto it then off I went.
2 weeks later I was called back to it as customer reported fridge temperature was at first too cold, then became warm. I suspected the evaporator may have been choked so I suggested a 48 hour defrost and to try it again and call me back if they have any further problems. Went back today as customer reported same problem so I investigated the freezers defrost system.
Heater tested ok and fan was ok, however when I checked the cube shaped toc that clips on the evaporator with 2 blue wires and 2 yellow wires on it I noticed that it was open circuit across the yellow wires and continuity across the blue wires. I have a gut feeling that both should be closed circuit. Does anyone know if this is the case before I order one up? Also, I have looked on Connect site and cant find the toc on its own. I can only find it with the defrost heater which isn’t very cheap.
Any help is very much appreciated!!!
Thanks,
Rob.