How to Check Refrigerant in a Central Air Unit

If your central air conditioner is struggling to keep your house cool, complete a pressure check test on your control unit to determine the level of refrigerant it contains. If the pressure test reads low, you know that the refrigerant inside the unit has leaked out. You can purchase a pressure test kit at most HVAC suppliers. However, every unit requires a different level of pressure so it is important to have the user manual for your HVAC unit handy so you know what the pressure for your particular unit should be.

HVAC pressure test kit
Owner's manual for HVAC air conditioner

Instructions

- 1
  Thread the coupler of the low pressure gauge, also known as the compound gauge, onto the low pressure valve mounted onto the HVAC unit. Although you have several valves mounted on your HVAC unit, the low pressure gauge, which is blue, will only fit on the low pressure valve.
- 2
  Thread the coupler of the high pressure gauge into the high pressure valve mounted onto the HVAC unit. Again, the high pressure gauge, which is red, will only fit on the high pressure valve.
- 3
  Inspect the gauges for the high pressure valve and for the low pressure valve. You will see several rows of numbers around the gauges. The numbers you need are labeled in black and red.
- 4
  Compare the numbers on the pressure gauges to the specified tolerances for your HVAC unit listed in your owner's manual. If the numbers on the gauges read lower than required, consult a trained technician to troubleshoot leaks in your unit.

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