Rowe 548 food machine. Can't keep machine operating. Feel like I have replaced all the parts internally (so does my wallet). Machine cools after servicing, but can't reach 45 degrees within the 30 minute allotment. Reset the time delay and finally will get down below 45, but the condensor will freeze solid. Replaced thermostat, relays (even wired around them). New compressor, fan motor and evaporator motor. Help!