6–3 T-349Will not initiate defrostmanuallyManual defrost switch defective ReplaceDefrost temperature sensor open 5.10.4Initiates but relay (DR)drops out Low line voltage 3.3Initiates but does not defrost Heater contactor or coil defective ReplaceHeater(s) burned out 7.15Frequent defrost Wet load Normal6.7 ABNORMAL PRESSURES (COOLING)High discharge pressureCondenser coil dirty 7.10Condenser fan rotating backwards 7.11Condenser fan inoperative 7.11Refrigerant overcharge or noncondensibles 7.7.1Discharge pressure regulator valve defective 7.20Discharge service valve partially closed OpenSuction modulation valve malfunction 7.19Low suction pressureSuction service valve partially closed OpenFilter-drier partially plugged 7.13Low refrigerant charge 7.7.1Expansion valve defective 7.14No evaporator air flow or restricted air flow 7.15Excessive frost on evaporator coil 6.6Evaporator fan(s) rotating backwards 7.16Discharge pressure regulator valve defective 7.20Suction modulation valve malfunction 7.19Suction and dischargepressures tend to equalizewhen unit is operatingHeat exchanger defective ReplaceCompressor valves defective 7.8Compressor cycling/stopped Check6.8 ABNORMAL NOISE OR VIBRATIONSCompressorLoose mounting bolts TightenWorn bearings 7.8Worn or broken valves 7.8Liquid slugging 7.14Insufficient oil 7.8.6Condenser or Evaporator FanBent, loose or striking venturi CheckWorn motor bearings 7.11/7.16Bent motor shaft 7.11/7.16CONDITION POSSIBLE CAUSEREMEDY/REFERENCESECTION
