Fault was fridge not cooling due to evap,fan and defrost tray heater choked – up,defrosted fully,cleared drain channel and tested both heaters,sensors,thermal fuse and fan all ok.I replaced the lower back panel in fridge due to damage and advised customer all should be ok.A week or so later customer back on saying still not cooling,i call back to find it is cooling to some extent but displaying 20c (which it wasnt) and the defrost tray heater was froze over again.I forced both heaters to come on but nothing from the tray heater.Ive now replaced Tray Heater,both sensors and main pcb but prob still persists(fan is working).If anyone has any ideas it would be much appreciated. Dan