How to Use C-manifold Gauges on Home Air Conditioning

Air conditioners remove the moisture from the air inside your home in order to cool the residence. If you are having problems with your air conditioner, you can use a C-manifold gauge to check the refrigerant pressure in the system. These gauges give you a reading in pounds per square inch (PSI). Although you can check the refrigerant pressure yourself, a licensed HVAC technician should ultimately handle the repairs to your AC unit.

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Use C-manifold gauges to diagnose problems with your AC unit.

Step 1

Turn on the AC unit at the thermostat and allow it to run for about 20 minutes then turn it off.

Step 2

Connect the blue gauge on the C-manifold to the low side service port on the AC unit. The low side is the larger pipe coming out of the unit.

Step 3

Connect the red gauge to the high side service port on the AC unit. The high side is the smaller pipe on the unit.

Step 4

Open the gauges to get the PSI readings on your unit. Write down the pressure readings from the blue and red gauges. If the low side pressure is between 28 and 30 PSI, there should be cool air coming from the vents in the inside of your home. If the air is not cool, consult a licensed HVAC technician to diagnose the problem.

Step 5

Check the high side pressure. This pressure should be around two times the temperature of the air inside the home. For example, if the temperature inside your home is 70 degrees, then the PSI should be around 140. Consult a licensed HVAC technician if the pressure is higher or lower.