Maytag MFI2266AES Service Manual - Page 28

System Diagnosis the high side (condenser) of the system. To diagnose for a restriction versus a refrigerant • Only partial frosting of evaporator instead of even shortage, discharge the system, replace the drier-filter, frosting of entire coil. evacuate and recharge with the specified refrigerant charge. If the unit performs normally three possibilities NOTE 1: Usually the first thing that is noticed by the user is a rise in temperature foods. Although temperatures will rise in both the freezer section and the food compartment, the frozen meats and vegetables will not thaw immediately. The customer doesn't associate the problem with the freezer section and will first notice that milk and other food beverages are not cold enough. Under some circumstances, such as in the case of forced air meatkeeper model with a slight shortage of refrigerant, freezing in the food compartment may be experienced due to the additional running time. With a refrigerant leak, however, it always gets worse and as the refrigerant charge decreases the temperature will continue to rise. With a shortage of refrigerant the capillary line will not have a full column of liquid. As a result, there is a noticeable hissing sound in the evaporator. This should not be mistaken for the regular refrigerant boiling sounds that would be considered normal. exist: 1) refrigerant loss, 2) partially restricted drierfilter, and 3) moisture in system. If the unit performs as it previously did you may have a restricted capillary line or condenser or kinked line. Find the point of restriction and correct it. A restriction reduces the flow rate of the refrigerant and consequently reduces the rate of heat removal. Complete restriction may be caused by moisture, solid contaminants in the system, or a poorly soldered joint. Moisture freezes at the evaporator inlet end of the capillary tube or solid contaminants collect in the drierfilter. The wattage drops because the compressor is not circulating the usual amount of refrigerant. As far as pressure readings are concerned, if the restriction, such as a kinked line or a joint soldered shut is anywhere on the low side, the suction pressure would probably be in a vacuum while the head pressure will be near normal. If the restriction is on the high side, the suction pressure, again, will probably be in a vacuum while the head pressure will be higher than normal during the pump out period described earlier. In either case, it will take longer than the normal ten minutes or so for the head pressure to equalize with the low side Symptoms of a Restriction after the compressor stops. Always remember refrigeration (cooling) occurs on the low pressure side of a partial restriction (obviously a total restriction will completely stop the circulation of refrigerant and no cooling will take place). Physically feel the refrigeration lines when a restriction is suspected. The most common place for a restriction is at the drier-filter or at the capillary tube inlet or outlet. If the restriction is not total there will be a temperature difference at the point of restriction, the area on the evaporator side will be cooler. In many cases frost and/ or condensation will be present. A longer time is required for the system to equalize. Symptoms of Air in System This can result from a low side leak or improper servicing. If a leak should occur on the low side, the temperature control would not be satisfied; thus, continuous running of the compressor would result. The compressor would eventually pump the low side into a vacuum drawing air and moisture into the system. Air and R134A do not mix so the air pressure would be added to the normal head pressure, resulting in higher than normal head pressures. Any kinked line will cause a restriction so the entire system should be visually checked. One way to determine if air is in the system is to read the head pressure gauge with the product off and A slight restriction will give the same indications as a evaporator and condenser at the same temperature and refrigerant shortage with lower than normal back then take the temperature on the condenser outlet tube. pressure, head pressure, wattage and warmer product This temperature should be within 3° or 4° F. of what the temperatures. Pressure-Temperature Relation chart shows for the NOTE 2: If a total restriction is on the discharge side of the compressor, higher than normal head pressures and wattages would result. This is true only while the low side is being pumped out and if the restriction was between the compressor and the first half of the condenser. given idle head pressure. If the temperature of the condenser outlet is considerably lower than the idle head pressure of the gauge this would indicate there is air in the system. Thorough leak checking is necessary. Correct the source of the leak. Do not attempt to purge off the air because this could result in the system being undercharged. It is best to discharge, replace drier, evacuate and recharge with the specified refrigerant charge. 28 16026312 ©2006 Maytag Services