When a residential unit runs warmer than normal (or does not cool), the problem can be due to a leak or a restriction in the system or several other reasons. Check the following before conducting this test: (a) condenser fan, (b) evaporator fan, (c) door gasket, (d) linted condenser, (e) cabinet light (Does it stay on while door switch is depressed?), (f) cold-control (thermostat) settings, (g) high ambient and frequency of cabinet door openings by customer, and (h) defrost system (timer, termination switch, heater).
If items a through h are working correctly, begin the test:
1. Connect power to unit.
2. Install a piercing valve on the suction line and connect it to the compound gauge hose.
3. While the unit operates, check the pressure in the suction line (with the valve on the gauge closed.)
4. If the suction pressure reads above zero, stop the test. The problem is an inefficient compressor which must be replaced.
5. If the suction pressure reads below zero (a vacuum), continue the test to step 6.
6. Look to see if the last pass of the capillary tube, the drier, or the condenser is sweating or cold.
If so, the problem is a restriction in the system.
7. If the entire condenser feels cool to the touch, the problem can be a restriction or a complete loss of refrigerant. Add refrigerant to the system. If the temperature rises throughout the condenser, the problem is a leak. Otherwise, there is a restriction in the system.
8. If the last pass of the capillary tube, drier, or the condenser feels warm, the problem is a leak.
If there is a restriction in the system, replace the drier, evacuate, and recharge the system. If there is a leak, locate and seal the leak, replace the filter-drier, evacuate, and recharge the system.