Maytag MFI2266AES Service Manual - Page 13
Warning, Caution
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Service Procedures ! WARNING To avoid risk of electrical shock, personal injury, or death, disconnect electrical power source to unit, unless test procedures require power to be connected. Discharge capacitor through a 10,000 ohm resistor before attempting to service. Ensure all ground wires are connected before certifying unit as repaired and/or operational. Restrictions Symptoms Restrictions in sealed system most often occur at capillary tube or filter drier, but can exist anywhere on liquid side of system. Restrictions reduce refrigerant flow rate and heat removal rate. Wattage drops because compressor is not circulating normal amount of refrigerants. Common causes of total restrictions are moisture, poorly soldered joints, or solid contaminants. Moisture freezes at evaporator inlet end of capillary tube. Solid contaminants collect in filter drier. If restriction is on low side, suction pressure will be in a vacuum and head pressure will be near normal. If restriction is on high side, suction pressure will be in a vacuum and head pressure will be higher than normal during pump out cycle. Refrigeration occurs on low pressure side of partial restriction. There will be a temperature difference at the point of restriction. Frost and/or condensation will be present in most cases at the point of restriction. Also, system requires longer to equalize. Slight or partial restriction can give the same symptoms as refrigerant shortage including lower than normal back pressure, head pressure, wattage, and warmer temperatures. Total restriction on the discharge side of compressor, when restriction is between compressor and first half of condenser, results in higher than normal head pressure and wattage while low side is being pumped out. Testing for Restrictions To determine if a restriction exists: 1. Attach gauge and manifold between suction and discharge sides of sealed system. 2. Turn unit on and allow pressure on each side to stabilize. Inspect condenser side of system. Tubing on condenser should be warm and temperature should be equal throughout (no sudden drops at any point along tubing). • If temperature of condenser tubing is consistent throughout, go to step 4. • If temperature of condenser tubing drops suddenly at any point, tubing is restricted at point of temperature drop (if restriction is severe, frost may form at point of restriction and extend down in direction of refrigerant flow in system). Go to step 5. 3. Visually check system for kinks in refrigeration line which is causing restriction. Correct kink and repeat step 2. 4. Turn unit off and time how long it takes high and low pressure gauges to equalize: • If pressure equalization takes longer than 10 minutes, a restriction exists in the capillary tube or drier filter. Go to step 5. • If pressure equalization takes less than 10 minutes, system is not restricted. Check for other possible causes of malfunction. 5. Recover refrigerant in sealed system. NOTE: Before opening any refrigeration system, capture refrigerant in system for safe disposal. 6. Remove power from unit. ! CAUTION To avoid risk of personal injury or property damage, take necessary precautions against high temperatures required for brazing. 7. Remove and replace restricted device. 8. Evacuate sealed system. 9. Charge system to specification. NOTE: Do not use captured or recycled refrigerant in units. Captured or recycled refrigerant voids any compressor manufacturer's warranty. NOTE: Charge system with exact amount of refrigerant. Refer to unit nameplate for correct refrigerant charge. Inaccurately charged system will cause future problems. ©2006 Maytag Services 16026312 13