Food in bottom of fridge (second hand SR-S20NTD) was freezing; tried various fixes (details added) and now have flashing beeping lock display.. T

Your fridge is telling you there is a fault, i'd say one of the 2 fans are not working. If everything is freezing in the bottom of the food compartment then the upper fan is faulty. You have to remove the shelves & remove the rear panel, the fan is in the shute at the bottom, remove, repair the broken wire or replace. Make sure unit is unpluged.

Keep your hand on condenser coil if it's visible or left and or right side body of the fridge. If you feel hot the gas is o.k. Otherwise no gas or chock. You have to repair and refill the gas.

bad control panel common problem

the beeping is an alarm certain lights on the display will be flashing when it is beeping record which lights are flashing this idicates a fault code then post your results and i will tell you what the fault code is and what the problem is likely to be :)

If the cabinet is warm inside it is a failed circulation fan, failed defrost causing the evaporator to freeze up, or it needs a refrigerant gas top up.

Beeping is just an alarm. It may be because of the more serious issues listed above but can also be caused by a failing door gasket, the door being left ajar (kids are famous for this) or the door has been left open too long deciding what to have for dinner.

I hope that answers all 8 of you :>D

Help here

https://www.google.com/search?q=fisher+and+paykel+fridge+beeping+with+door+shut

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on the main circuit board on top of the fridge is a button with "test" on it. hold that in for a few sec, it should start beeping at you. push it again and it will beep again, do this about 4 time till it goes quite. this may fix it but the reason for it is prob your sensor is covered in ice, you need to leave it off with the doors open. there are 2 drain pipes at the back of the fridge ( bottom ) defrost it till no more water comes out of these, when you think its done, leave it for a few more hours and if any water comes out your not defrosted yet--- mine took almost 3 days.

Adjust the temperature control for the freezer to a normal setting. Fast freeze is only for when new products are put in that need to be frozen. This locks the system into a continuous run mode and could be responsible for the freezing condition in the refrigerator section. Check the temperatures with a thermometer as the sensor for the freezer temperature could be bad causing the light to come on.

Sounds like the damper isn't closing or the thermostat isn't working. I've seen these dampers freeze open and it basically turns your food side into a freezer side! Look at part #115 on this site. Take a mirror and look way back in the upper corner to see if you can see the little damper window is open, I'll bet it is staying open all the time pushing the freezer air into your fresh food side. http://tinyurl.com/5bnk6f.

You most likely have a problem in the freezing/cooling circuit. Check your condenser, evaporator fans to see if they are running okay. Most likely it may be the condenser fan.