Fisher & Paykell freezer problem

[jack in oz]

This is my first post and I would appreciate some advice.

I have a Fisher & Paykell model N210 freezer. A few months ago it wasn't freezing. After doing some research on this forum I determined that the defrost element had failed. I replaced it and the freezer seemed to be working again. I confirmed that the defrost heater was working by rotating the defrost timer to the defrost position and measuring the power consumption. It read 330 watts.


Over 2 months the freezer has been gradually getting warmer to the point where it wouldn't freeze water. I manually defrosted the freezer and it released enough water to overflow the collection tray twice. I immediately suspected the heater had failed again. However, I checked it with a multimeter and it reads 190ohms.


I then suspected the thermostat, so I removed it and 'froze' it in my other freezer. I removed it from my freezer and checked the contacts with the multimeter. The contacts were closed. After a few minutes at room temperature there was a ''click'' as the contacts opened. I guess that means the thermostat is OK.


I'm now suspecting the defrost timer is the problem. I rotate the timer with a screwdriver until I hear a loud 'click' and the compressor cuts out. However the heater element isn't being powered.
I guess it could also be a faulty wiring connector in the timer-thermostat-heater circuit. I'd like to check the timer is definitely faulty before I buy a new one.


The freezer is currently running at -13C according to my thermocouple probe. That's with the temp controller set to 7 (full cold).


I would appreciate any help.


Regards,
Jack

[jack in oz]

I'm really confused now!


I just went back to the freezer. Internal temp measuring +2C. Opened freezer and the heater element is warm and there's water in the collection tray at the rear of the cabinet. I'm now wondering if the thermostat is letting the defrost heater run for too long and this is warming the cabinet up too much?

[jack in oz]

Ignore my second post. Temp recovered very quickly to -18C.

Back to my original question- how do I check the defrost timer is working properly?

[tonto33]

Test the defrost timer with a multi meter Clip one probe to each defrost timer -- not motor -- wire, and turn the timer control screw shaft until it clicks. If the defrost timer is functioning, the meter will read zero. If the needle jumps, the defrost timer is faulty. Replace it with a new one of the same type.

[jack in oz]

Thanks Tonto,
the freezer seems to be working now. It's successfully been thru 3 defrost cycles now. I'm wondering if the timer motor is unreliable or the mechanism is jamming. Perhaps I loosened up the timer when I rotated it with the screwdriver? I'll keep an eye on it for now.
Cheers