Hotpoint Mistral Displaying wrong temp for freezer

[sme22]

Hi - lady in distress!

I have a Hotpoint Mistral fridge freezer - having thrown away food before thinking it had defrosted and frozen again I now discover that the two freestanding thermometers I have put in the freezer both register lower than -30 degrees - the food also is quite frozen - BUT the display at the top of the freezer is telling me at diffrerent times of day anything between +14 to +4 at the moment.
The fridge temp is fine - had a thermistor about 18 months ago replaced for that as fridge was freezing everthing. Should I worry or just ignore the temperature display from now on? This has happened 3 times now - the previous two I turned it off for a few days as advised by a friend and chucked the contents - as it is not my main fridge freezer it is a problem but not critical. Anyone got any suggestions or had this problem before? Apart from these episodes it works fine the rest of the time. Thanks in anticipation of a reply with the solution.

[spimps]

If you don't want to repair/spend on it you could buy a thermometer especially for a freezer which has a wired sensor and an audible alarm.just clamps to the side or top and the sensor goes inmate the freezer.http://fridge-freezer-alarm.co.uk/ may have something,tons available on net.
BG

[HotpointCarl]

change thermistors common thing and cheap and easy to do.