If the freezer is rising up to -12 and then dropping back down to -21 then it sounds like there is a problem here.
As a freezer should just maintain a temperature so may drop a deg and raise a deg above what you have set but it shoulded rise a lot like -12 so if its doing this there is a fault with that.
As this is a frost free appliance what you can try is a full defrost. If you can move the freezer contents some were else and then turn the appliance off for 24 hours and leave the freezer door open. As if the evaporator gets blocked with to much ice it can cause faults like this.
So when its defrosted fingers crossed this cures it. But as to your question no this isn't correct as it should rise like this to -12.
If you need anymore info just get back to me.
thanks for the advise....having left it on longer it now fluctuates from -14 to -21 but I guess this is still a problem .I have read a report that this kind of fluctuation can happen to a frost free freezer . If this is not cured with a full defrost what is the likely problem and cost?
If the defrost doesn't cure it then its possibley the control unit. As its getting to -21 so the compressor is working and the gas will be fine so that just leaves the control unit as it has relays on there and sometimes these can stick so it doesn't bring the compressor straight back on when it should.
Thanks....so if its a control unit problem what is the likely cost or should I but a new fridge freezer even though its only 6 years old.
The control board on these are about £70 then theres labour if you are getting someone In to do this so labour is roughly about £50 so for a repair you are looking at about the £120 mark roughly so its not bad considering the price of a new appliance is roughly £300-400.
why do you think the breaker on the fuse box tripped originally?
The breaker could have tripped out to anything. Theres a lot of reasons why they trip out.
Did a light bulb blow?
Posibbley an over load on circuit, It could be a number of things im afraid.