Why Does My Air Conditioner Have High Pressure on the Suction Side?

Dirty Coils

• If your evaporator coils are dirty or covered with frost, they will not be able to properly rid the refrigerant of heat. The result is refrigerant that cycles through the system inefficiently, without changing temperature or state enough to cool the air as the correct speed. This can lead to progressively higher pressures on the suction side compared to the already-high pressure in the other refrigerant lines. Cleaning the coils can help solve this problem.

Overcharging

• Overcharging refers to adding too much new refrigerant to an air conditioner system. Too much refrigerant can cause pressure problems like high pressure on the suction lines. This impairs the ability of the air conditioner to operate correctly and can lead to serious problems with compressors. Your system may make rattling noises or vibrate if it is overcharged. Some of the refrigerant needs to be drained to restore the air conditioner to proper operation.

Other Charging Problems

• Sometimes, other charging issues may also cause high pressures in evaporator-side refrigerant lines. Your lines may not be overcharged, but air could have been trapped in the system if you recently had a leak repaired. This air may be responsible for the pressure issues and needs to be drawn out of the lines. The air also has moisture in it, which can freeze and cause further pressure problems.

Valve Issues

• Refrigerant pressure is also determined by the valves that control the system and regulate when the refrigerant moves through various components. If valves fail or become frozen, they may be stuck in the wrong position. That can lead to a build-up of refrigerant. Measuring pressure along the refrigerant line can pinpoint problems, but it requires specific gauging systems and skill in using them. If you do not have a lot of experience in diagnosing refrigerant problems, leave this step to the professionals.