If the low-side pressure is 90 psi and the high-side is 250 psi, what is the most likely problem?

If the low-side pressure is 90 psi and the high-side is 250 psi, what is the most likely problem?

• A. Undercharged system
• B. Overcharged system
• C. Inefficient compressor
• D. Leaking evaporator

Answer: (C)

Focus on how the pressures tell you about how well the compressor is moving refrigerant. The high-side pressure (discharge side) is 250 psi, which is quite elevated, while the low-side (suction side) is 90 psi, already higher than what you’d expect from a normal, properly charged system under typical cooling load. That combination points to the compressor not delivering refrigerant efficiently. If the compressor isn’t pumping gas effectively (due to wear, bad valves, or other mechanical issues), you can get a high discharge pressure because the refrigerant is being compressed less efficiently, while the suction side doesn’t fall as low as it should because not enough vapor is being drawn from the evaporator. In other words, the system is producing pressure but not moving refrigerant well, which is characteristic of an inefficient or worn compressor. Undercharged would mostly show low pressure on both sides, overcharged would raise pressures but would not typically present with this specific mismatch, and a leaking evaporator would usually show a notably low suction pressure due to refrigerant loss.

Focus on how the pressures tell you about how well the compressor is moving refrigerant. The high-side pressure (discharge side) is 250 psi, which is quite elevated, while the low-side (suction side) is 90 psi, already higher than what you’d expect from a normal, properly charged system under typical cooling load.

That combination points to the compressor not delivering refrigerant efficiently. If the compressor isn’t pumping gas effectively (due to wear, bad valves, or other mechanical issues), you can get a high discharge pressure because the refrigerant is being compressed less efficiently, while the suction side doesn’t fall as low as it should because not enough vapor is being drawn from the evaporator. In other words, the system is producing pressure but not moving refrigerant well, which is characteristic of an inefficient or worn compressor.

Undercharged would mostly show low pressure on both sides, overcharged would raise pressures but would not typically present with this specific mismatch, and a leaking evaporator would usually show a notably low suction pressure due to refrigerant loss.