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    Gauge Diagnostics

    Using Gauges for Troubleshooting

    Gauge pressure is the first tool in AC troubleshooting. The table below shows 7 Gauge Readouts that you may encounter. Use the Gauge Readout Tool separately or in combination with the table of Gauge Diagnostics for AC troubleshooting.

    Gauge Readout Tool

    Normal Conditions
    Air in cooling system (insufficient suction)
    Defective expansion valve
    Excessive refrigerant
    Moisture Intrusion
    Refrigerant does not circulate
    Summary Table of Gauge Diagnostics

    Normal Conditions

    1 Atmosphere
    Room Temperatures of 30-38 C (86 - 96 F)
    Engine speed of approx. 1500 rpm or about 75% of rated engine speed

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    Air in cooling system (insufficient suction)

    Pressure Range
    Low side: 36 to 50 psi
    High side: 284 to 356 psi
    Indications
    Both pressures are TOO HIGH
    The low-side piping is not cold
    Causes
    Air in the system
    Remedy
    Evacuate the system
    Replenish the refrigerant
    Check the gauge readings
    If prolonged operation with air in the system, the liquid tank must be replaced.

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    Defective expansion valve

    Pressure Range
    Low side: 30 to 36 psi
    High side: 313 to 327 psi
    Indications
    Both pressures are TOO HIGH
    Causes
    Improper refrigerant charge
    Defective expansion valve
    Improper temperature sensor installation
    Remedy
    Verify refrigerant charge
    Check temperature sensor installation and insulation
    If the refrigerant charge is okay and the temperature sensor installation and insulation are correct then replace the expansion valve.

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    Excessive refrigerant

    Pressure Range
    Low side: 36 to 43 psi
    High side: 327+ psi
    Indications
    Both pressures are TOO HIGH
    Causes
    Pressure increase due to excessive refrigerant
    Insufficient condenser cooling
    Remedy
    Verify the refrigerant level
    Clean the condenser
    Check and adjust the fan belt and / or the condenser fan motors

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    Moisture Intrusion

    Pressure Range
    Low side: 18 to 28 psi
    High side: 85 to 256 psi
    Indications
    Low pressure side alternates between a vacuum and normal pressure
    Causes
    Moisture has frozen in the air conditioner system, clogging the expansion valve.
    Remedy
    Evacuate the system
    Replace the receiver dryer
    Recharge the system

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    Refrigerant does not circulate

    Pressure Range
    Low side: 0 to -29.99 psi
    High side: 71 to 85 psi
    Indications
    Low pressure side becomes a vacuum
    High pressure as listed above
    Frost or condensation on the front and rear pipe connections of the receiver dryer or expansion valve
    Causes
    AC system is blocked by contamination or ice
    AC system is shut off by defective expansion valve or tempeerature sensor
    AC line from evaporator to compressor has kink in the line
    Remedy
    STOP OPERATION IMMEDIATELY
    Check for contamination or ice
    If moisture is found then evacuate the system
    If the expansion valve is defective then replace it
    Replace receiver dryer
    Recharge with refrigerant to proper level
    Repair any kinked hoses

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    Summary Table of Gauge Diagnostics

     Low Pressure Side is TOO HIGH
    The low pressure side normally becomes too high when the high pressure side is too high.

    Cause Inspection Remedy
    Defective Thermoswitch The magnetic clutch switch turns off before the outlet air temperature is sufficiently low. Replace the thermoswitch
    Poor Expansion Valve
    temperature sensor contact
    The high and low pressure sides gauge pressures equalize when the magnetic clutch is turned off (within a short time duration) Replace Compressor
    Expansion Valve opens too far Frost has adhered to the suction hose / pipe Install the temperature sensor against the low pressure pipe and cover with insulating tape.
    Clogged compressor suction filter Compressor fitting is cool but the low pressure hose is not. Remove and clean the filter.


    Low Pressure Side is TOO LOW

    Cause Inspection Remedy
    Insufficient Refrigerant There is little temperature difference between the low and high pressure sides. Repair any leaks and recharge the refrigerant to the correct levels.
    Clogged liquid tank
    (receiver dryer, accumulator)
    Considerable temperature difference between the inlet and outlet sides of the receiver dryer during operation. Also, tank may be frosted Replace liquid tank (receiver dryer)
    Clogged expansion valve Expansion valve inlet side is frosted. Generally the low side pressure is near vacuum. Replace expansion valve.
    Expansion valve temperature
    sensor gas leak
    (damaged capillary tube, etc..)
    Expansion valve outlet side is chilled and low pressure side is LOW. Clean or replace expansion valve.
    Clogged or blocked piping Low pressure readings decrease or a negative reading is shown. Indicates piping is clogged or blocked between the evaporator coil and the compressor. A frost spot may indicate the point of blockage. Clean or replace piping.
    Defective thermoswitch
    (cold control)
    Evaporator is frozen showing ice along the face of the coil, not just frost on the manifolds of the coil. Adjust temperature sensing tube to a cooler part of the coil or replace the thermoswitch.


    High Pressure Side is TOO HIGH

    Cause Inspection Remedy
    Poor Condenser cooling Dirty or clogged condenser fins, Cooling fans do not operate correctly. Clean and / or repair the condenser core / fans.
    Excessive refrigerant Verify by gauge reading Utilize your refrigerant recovery equipment to capture excess refrigerant. Charge to the correct refrigerant levels.
    Air in the system Pressure is high on both high and low sides Evacuate, vacuum and recharge with refrigerant.


    High Pressure Side is TOO LOW

    Cause Inspection Remedy
    Insufficient refrigerant Little temperature difference between the low and high pressures. Repair any leaks and recharge the refrigerant to the correct levels

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    Perrin Manufacturing is committed to providing you with superior products and services; we renew this pledge through continual improvement of our products and motivation of our staff.

    ISO 9001:2015

    We faithfully comply with all of the requirements of our ISO 9001:2015 Quality Management System, the most current edition of the standard. Beyond that, our highly trained quality staff persistently search for new ways to improve the effectiveness of our system.

     

    Related Sites

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    PowerCubeapu.com

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    5610 Perkins Road
    PO Box 740 
    Alliance, NE 69301
    + 1 308 762 2975

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