To troubleshoot this type of air-conditioning equipment, a troubleshooting table (Table 15-1) has been provided at the end of this chapter. The general troubleshooting procedures listed in the table are used for hermetically sealed compressors.
Table 15-1 Troubleshooting Hermetic Compressor Type Air-Conditioning Equipment
| Trouble | Probable Cause | Remedy or Repair |
| Compressor will not start. (No hum.) | Open line circuit. | Check the wiring, fuses, and receptacle. |
| Protector open. | Wait for reset. Check current drawn from line. | |
| Contacts open on control relay. | Check control, and check pressure readings. | |
| Open circuit in the motor stator. | Replace the stator or the whole compressor. | |
| Compressor will not start. However, it hums intermittently. Cycles with the protector. | Not wired correctly. | Check wiring diagram and actual wiring. |
| Line voltage low. | Check line voltage. Find where line voltage is dropped. Correct. | |
| Start capacitor open. | Replace start capacitor. | |
| Relay contacts do not close. | Check by manually operating. Replace if defective. | |
| Start winding open. | Check stator leads. Replace compressor if the leads are OK. | |
| Stator winding grounded. | Check stator leads. Replace compressor if leads are OK. | |
| Discharge pressure too high. | Remove cause of excessive pressure. Discharge shutoff and receiver valves should be open. | |
| Compressor too tight. | Check oil level. Correct the binding cause. If this cannot be done, replace compressor. | |
| Start capacitor weak. | Replace the capacitor. | |
| Compressor starts. Motor will not speed up enough to have start winding drop out of circuit. | Line voltage low. | Increase the voltage. |
| Wired incorrectly. | Rewire according to wiring diagram. | |
| Relay defective. | Check operation. If defective, replace. | |
| Run capacitor shorted. | Disconnect the run capacitor and check for short. | |
| Start and run windings shorted. | Check winding resistances. If incorrect, replace the compressor. | |
| Start capacitor weak. | Check capacitors. Replace those defective. | |
| Discharge pressure high. | Check discharge shutoff valves. Check pressure |
|
| Tight compressor. | Check oil level. Check binding. Replace if necessary. | |
| Compressor starts and runs. However, it cycles on the protector. | Low line voltage. | Increase the voltage. |
| Additional current being drawn through the protector. | Check to see if fans or pumps are wired to the wrong connector. | |
| Suction pressure is too high. | Check compressor. See if it is the right size for the job | |
| Discharge pressure is too high. | Check ventilation. Check for over-charge. Also check for obstructions to air flow or refrigerant flow. | |
| Protector is weak. | Check current. Replace protector if it is not clicking out at right point. | |
| Run capacitor defective. | Check capacitance. Replace if found defective. | |
| Stator partially shorted or grounded. | Check resistance for a short to the frame. Replace if found shorted to ground (frame). | |
| Inadequate motor cooling. | Correct air flow. | |
| Compressor tight. | Check oil level. Check cause of binding. | |
| 3 phase line unbalanced. | Check each leg or phase. Correct if the voltages are not the same between legs | |
| Discharge valve leaks or is damaged. | Replace the valve plate. | |
| Start capacitors burn out. | Short cycling. | Reduce the number of starts. They should not exceed 20 h. |
| Prolonged operation with start winding in circuit. | Reduce the starting load. Install a crankcase pressure limit valve. Increase low voltage if this is found to be the condition. Replace the relay if it is found to be defective. | |
| Relay contacts sticking. | Clean the relay contacts. Or, replace the relay. | |
| Wrong relay or wrong relay setting. | Replace the relay. | |
| Wrong capacitor. | Check specifications for correct size capacitor. Be sure the MFD and WVDC are correct for this compressor. |
|
| Working voltage of capacitor too low. | Replace with capacitor of correct WVDC. | |
| Water shorts out terminals of the capacitor | Place capacitor so the terminals will not get wet. | |
| Run capacitors burn out. They spew their contents over the surfaces of anything nearby. This problem can usually be identified with a visual check. | Excessive line voltage. | Reduce line voltage. It should not be over 10% of the motor rating. |
| Light load with a high line voltage. | Reduce voltage if not within 10% overage limit. | |
| Voltage rating of capacitor too low. | Replace with capacitors of the correct WVDC. | |
| Capacitor terminals shorted by water. | Place capacitor so the terminals will not get wet. | |
| Relays burn out. | Low-line voltage. | Increase voltage to within 10% of limit. |
| High-line voltage. | Reduce voltage to within 10% of the motor rating. | |
| Wrong size capacitor. | Use correct size capacitor. The proper MFD rating should be installed. | |
| Short cycling. | Decrease the number of starts per hour. | |
| Relay vibrating. | Make sure you mount the relay rigidly. | |
| Wrong relay. | Use the recommended relay for the compressor motor. |
