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Inspecting air conditioning systemsAir conditioning is important for the comfort of your family especially on  hot and muggy days. Inspecting air conditioning systems is important to ensure satisfactory operation, if it’s not too cold out a good home inspector will run the air conditioning system to ensure it is working well. However if the outdoor temperature has been below 60 or 65 degrees within the past 48 hours, most often home inspectors do not run the air conditioning system since there is potential for damage to the equipment if it is too cold. In that case Home inspectors do a visual inspection of the components only. The conventional whole house air conditioning system is usually part of the forced air heating system, if so it will most often use the furnace blower fan and duct system to distribute the conditioned air. See the articles on forced air heating systems for information on the furnace and duct work cover will not cover the forced air furnace and duct work. In addition to identifying defects and needed repairs our inspection reports include a lot of maintenance tips and recommendations.

The 10 Most Common Defects I Find Inspecting Air Conditioning Systems

  1. Not Cooling Well – After the unit has run for about 30 minutes or more you can usually tell pretty well by feeling the air temperature at the duct how well the system is working. There are many variables but generally you want at least an 8 to 10 degree temperature drop between air going into the cold air return and coming out the cooling vent, or the unit may need repair.
  2. Sized Too Small – The functional operation and how well the system is sized for the house can be determined how quickly the central air conditioning system can bring down the temperature of the house. Again there are many variables here such as outdoor temperature, time of day, amount of insulation etc. If running all day a central cooling system should be able to keep the home “at least” 20 or more degrees below the outdoor temperature.
  3. Compressor Cabinet Not Level – Check level of the compressor housing. If too far out of level it can negatively affect the efficiency of the compressor and should be leveled.
  4. Dirty or Blocked Condenser Coils – Look at the air-conditioning coils for an accumulation of dirt or dust or grass clippings. Vacuum the coils to improve cooling efficiency. Try not to discharge grass clippings onto the coils.
  5. Damaged Insulation on Coolant Pipes – Inspect the insulation covering the coolant line into the house. If deteriorated or missing it should be replaced for improved efficiency.
  6. Open Gaps at Wall Penetrations – Check the wall penetration holes for the electric supply and cooling lines and caulk or seal any gaps or cracks. Mice can fit through a hole about 1/4 inch the approximate diameter of a pencil, not to mention cold air.
  7. Loud Noise – Check the compressor while it is running for loud or squeaky noises or loose parts and repair if needed.
  8. Rusty, Dented or Damaged Compressor Housing – In some installations it would be wise to install a protective cover on the compressor in winter months to protect from large ice falling off the roof.
  9. Dirty or Missing Air Filter at the Furnace –
  10. AC Will Not Turn On – If temperature allows, turn on the air conditioning with the cooling thermostat and check for correct operation. Make sure that the cooling system turns on and off at the preset temperatures.


The evaporator coil above the furnace is not visible unless the plenum is dissembled and is not normally inspected by home inspectors or home owners. An important part of Air conditioning maintenance is the changing of the furnace filter. If the air conditioning is run throughout the summer, the furnace filter should be changed every 30 to 60 days depending on the filter.