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Your Hotpoint frost-free appliance utilises a series of internal and external fans during its normal operation so there will be a slight increase in the operating noises. This is quite normal so do not worry if you hear one or two different sounds than those you heard with your old appliance.
If you are hearing a cracking noise then this is perfectly normal.
If you need further assistance please call Hotpoint customer service on 0344 822 4224.