Steps of Air Conditioning Repair in Philadelphia



In order to do your own air conditioning repair in Philadelphia you need to understand the unit’s sequence of operation. This is the order of events the system undergoes to cycle itself on and off. Knowing how the unit operates properly aids in determining where to start troubleshooting when the system doesn’t operate properly. Where the system varies from its normal sequence is a major clue to any problems.

Most of our calls for air conditioning repair in Philadelphia are simple fixes that can be done easily by homeowners but a few require knowledge of the operation of mechanical and electrical components of the system



  1. The compressor pumps out compressed high-pressure, superheated refrigerant vapor.


  1. Vapor passes through the outdoor finned condenser coil. Air from the outdoor fan removes heat from the refrigerant vapor. When enough heat is removed, the vapor condenses into a high-pressure liquid. The liquid temperature is slightly warmer than ambient air temperature.


  1. This warm, high-pressure liquid leaves the outdoor coil, and flows through the copper refrigerant liquid line.


  1. At the end of the liquid line, the refrigerant passes through a metering device, reducing its pressure and temperature.


  1. As the liquid, under reduced pressure, enters the indoor coil surface, it expands and absorbs heat from the indoor air passing over the finned surface. Heat, from the indoor air, causes the low-pressure liquid to evaporate and cools the indoor air. The refrigerant is now a cool vapor.


  1. Refrigerant vapor flows through the suction line to the compressor. The cycle then repeats.


The electrical cycle in order

  1. The thermostat calls for cooling.
  2. This sends a 24-volt signal through the “Y” terminal to the compressor contactor in the outdoor unit. The compressor and outdoor fan start.
  3. At the same time a 24-volt signal flows through the “G” terminal to the indoor blower relay. The indoor blower starts.
  4. The cooling system is now in operation.
  5. The thermostat satisfies and ends the call for cooling.
  6. This ends the 24-volt signal to the compressor contactor and the outdoor unit stops.
  7. This ends the 24-volt signal to the indoor blower relay and the indoor blower stops.
  8. The system is now off.


If you have any air conditioning repair questions and live in the greater Philadelphia area, feel free to contact us



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