Our 7 year old upright freezer quit running. We removed the food and let it set for 24 hours. There was no frost buildup anywhere. We plugged it back in and it started and ran for some time getting down to zero and shutting off. We put some frozen food in it and it started running. Some hours later the unit was not running and the digital display read 12 deg. We unplugged the unit and couple days later plugged it in and it immediately started running. Evap fan runs fine. Should I replace the control board?