Trouble Diagnoses for Abnormal Pressure

Gauge indication

Refrigerant cycle

Probable cause

Corrective action

Both high- and low-pressure sides are too high.

Courtesy of NISSAN NORTH AMERICA, INC.

Pressure is reduced soon after water is splashed on condenser.

Excessive refrigerant charge in refrigeration cycle

Reduce refrigerant until specified pressure is obtained.

Air suction by cooling fan is insufficient.

Insufficient condenser cooling performance

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1. Condenser fins are clogged.
2. Improper fan rotation of cooling fan

• Clean condenser.
• Check and repair cooling fan if necessary.

• Internal heat exchanger is not cold.
• When A/C compressor is stopped high-pressure value quickly drops by approximately 196 kPa (2 kg/cm ² , 28 psi). It then decreases gradually thereafter.

Poor heat exchange in condenser

(After A/C compressor operation stops, high-pressure decreases too slowly.)

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Air in refrigeration cycle

Evacuate and recharge system.

Engine tends to overheat.

Engine cooling systems malfunction.

Check and repair engine cooling system.

• An area of the low-pressure pipe is colder than areas near the evaporator outlet.
• Plates are sometimes covered with frost.

• Excessive liquid refrigerant on low-pressure side
• Excessive refrigerant discharge flow
• Expansion valve is open a little compared with the specification.

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Improper expansion valve adjustment

Replace expansion valve.

Gauge indication

Refrigerant cycle

Probable cause

Corrective action

High-pressure side is too high and low-pressure side is too low.

Courtesy of NISSAN NORTH AMERICA, INC.

Upper side of condenser and high-pressure side are hot, however, liquid tank is not so hot.

High-pressure tube or parts located between A/C compressor and condenser are clogged or crushed.

• Check and repair or replace malfunctioning parts.
• Check oil for contamination.

Gauge indication

Refrigerant cycle

Probable cause

Corrective action

High-pressure side is too low and low-pressure side is too high.

Courtesy of NISSAN NORTH AMERICA, INC.

High- and low-pressure sides become equal soon after A/C compressor operation stops.

A/C compressor pressure operation is improper.

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Damaged inside A/C compressor packings.

Replace A/C compressor.

No temperature difference between high- and low-pressure sides.

A/C compressor pressure operation is improper.

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Damaged inside A/C compressor packings.

Replace A/C compressor.

Gauge indication

Refrigerant cycle

Probable cause

Corrective action

Both high- and low-pressure sides are too low.

Courtesy of NISSAN NORTH AMERICA, INC.

• There is a big temperature difference between liquid tank outlet and inlet. Outlet temperature is extremely low.
• Liquid tank inlet and expansion valve are frosted.

Liquid tank inside is slightly clogged.

• Replace liquid tank.
• Check oil for contamination.

• Temperature of expansion valve inlet is extremely low as compared with areas near liquid tank.
• Expansion valve inlet may be frosted.
• Temperature difference occurs somewhere in high-pressure side.

High-pressure pipe located between liquid tank and internal heat exchanger is clogged.

• Check and repair malfunctioning parts.
• Check oil for contamination.

Expansion valve and liquid tank are warm or only cool when touched.

Low refrigerant charge.

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Leaking fittings or components.

Check refrigerant system for leaks. Refer to Leak Test .

There is a big temperature difference between expansion valve inlet and outlet while the valve itself is frosted.

Expansion valve closes a little compared with the specification.

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1. Improper expansion valve adjustment.
2. Malfunctioning expansion valve.
3. Outlet and inlet may be clogged.

• Remove foreign particles by using compressed air.
• Check oil for contamination.

An area of the low-pressure pipe is colder than areas near the evaporator outlet.

Internal heat exchanger is clogged or crushed.

• Check and repair malfunctioning parts.
• Check oil for contamination.

airflow volume is too low.

Evaporator is frozen.

• Check intake sensor circuit.

  Refer to Diagnosis Procedure .

• Repair evaporator fins.
• Replace evaporator.
• Refer to Component Function Check .

Gauge indication

Refrigerant cycle

Probable cause

Corrective action

Low-pressure side sometimes becomes negative.

Courtesy of NISSAN NORTH AMERICA, INC.

• Air conditioning system does not function and does not cyclically cool the compartment air.
• The system constantly functions for a certain period of time after A/C compressor is stopped and restarted.

Refrigerant does not discharge cyclically.

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Moisture is frozen at expansion valve outlet and inlet.

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Water is mixed with refrigerant.

• Drain water from refrigerant or replace refrigerant.
• Replace liquid tank.

Gauge indication

Refrigerant cycle

Probable cause

Corrective action

Low-pressure side becomes negative.

Courtesy of NISSAN NORTH AMERICA, INC.

Liquid tank or front/rear side of expansion valve's pipe is frosted or dewed.

High-pressure side is closed and refrigerant does not flow.

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Expansion valve or liquid tank is frosted.

Leave the system at rest until no frost is present. Start it again to check whether or not the malfunction is caused by water or foreign particles.

• If water is the cause, initially cooling is okay. Then the water freezes causing a blockage. Drain water from refrigerant or replace refrigerant.
• If due to foreign particles, remove expansion valve and remove the particles with dry and compressed air (not shop air).
• If either of the above methods cannot correct the malfunction, replace expansion valve.
• Replace liquid tank.
• Check oil for contamination.