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I have a fridge/freezer (Fisher and Paykel Model N500B, probably around 40 years old) - that I recently bought out of storage and installed in our kitchen. I tested it before installing it and it seemed fine - fridge at 4C, freezer around -18, but the freezer has decided to go warm - it sits at -5 to -10. I took the back wall plate off the freezer compartment and was presented with a large mass of ice. The fan was running no problem. I defrosted the ice from the evaporator and put it all back together and the freezer is now reaching -19C.

Does this indicate the defrost cycle isn't running? I'm currently logging the freezer temperature. Will the defrost cycles be evident on the temperature record if the defrost cycles are occurring?

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rossmcm
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  • can you read and understand the schematic ??? – Ruskes Jul 11 '22 at 06:09
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    it could be any of the following, Defrost time, thermal fuse, defrosting heater coil – Ruskes Jul 11 '22 at 06:12
  • I'm an EE so no issue for me with the schematic. My reading is that the fan only runs if the thermostat is closed and the defrost timer contact is to the left (which will cause the compressor to run). My thinking is a faulty timer or possibly a dead defrost element. – rossmcm Jul 11 '22 at 06:28
  • correct, the timer will stop the compressor and start the fan and heating coil – Ruskes Jul 11 '22 at 06:35
  • using ohm meter check the heating coil, but firts disconnect it – Ruskes Jul 11 '22 at 06:38
  • also check the thermal fuse – Ruskes Jul 11 '22 at 06:38
  • If you manage to fix your problem, keep an eye on electricity usage. Even if it cools properly, the insulation may have deteriorated and result in a significantly larger electricity bill. With fridges and freezers, it's often worth retiring decades old equipment in favour of something new and energy efficient. – MiG Jul 11 '22 at 06:46
  • @knowitall - just to clarify, you stated: `correct, the timer will stop the compressor and start the fan and heating coil` By my reading when the timer stops the compressor (i.e. when pin 1 of the timer is connected to pin 4) the fan will _not_ run, but the heating coil will be energised. When pin 1 is switched to pin 3 the compressor and the fan are both energised, but not the heater. Am I missing something? – rossmcm Jul 12 '22 at 05:23
  • After second look: The timer will stop the compressor and the fan and it will provide power to the defrost element, over the thermal switch if the <9C switch is in close postition – Ruskes Jul 12 '22 at 05:35
  • The timer will stop the compressor and the fan and it will provide power to the defrost element, over the thermal switch if the <9C switch is in close postition It is unclear if the thermal fuse is working, or the defrosting coil is broke – Ruskes Jul 11 '22 at 07:06

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