There are several symptoms that indicate the presence of an excessive amount of refrigerant in the system.
1. Long running time of the unit. When there is too much refrigerant in the system, the unit runs for an exceedingly long period of time before the temperature drops to the point where the thermostat becomes satisfied and shuts off the compressor. This increase in compressor running time is due to the increased pressure in the evaporator from overcharging. The more refrigerant charged into the system, the higher the head and back pressures go. (See the temperature-pressure chart on page 133).
2. Head and back pressures read higher than normal.
3. High temperatures in the freezer and fresh-food compartments. The customer complaint here is that the unit does not get as cold as it used to. This is true because the evaporator plates do not get as cold as they should.
4. Suction line near the compressor sweats or frosts up.
5. Compressor-operating amperage goes too high. Note the FLA (run amperage) on the nameplate (example: FLA 12). With the unit running, close the jaws of the flux-type ammeter around the wire going to the compressor run or common terminal. If the meter reads 18 A for example, the unit can be overcharged with refrigerant.
Look again at the section on “Signs of Loss of Refrigerant” (item number 3). By using an ammeter, it can be determined if the unit is overcharged with refrigerant (fig. 124). With the unit running and the ammeter placed around the run or common wire, a high amperage reading indicates an overcharge (too much refrigerant).