Carrier 38AU - User Manual

Questions and Answers

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brianarichardsonAug 14, 2025
Why is my Carrier 38AU compressor running but cooling insufficient?
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  Maria AustinAug 14, 2025
  If your Carrier Air Conditioner's compressor is running, but the cooling is insufficient, it could be due to: * Low suction pressure because of low refrigerant charge: Add refrigerant. * Low suction pressure because of low head pressure: Check refrigerant charge and outdoor-air fan thermostat settings. * Low suction pressure because of dirty air filters: Clean or replace the filters. * Low suction pressure because of a defective expansion valve power head: Replace the power head. * Low suction pressure because of a partially iced indoor coil: Check the low-pressure setting. * Low suction pressure because of restricted indoor airflow: Remove the obstruction. * High suction pressure because of excessive heat load: Check for open doors or windows near the fan coil.
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Lisa LarsonAug 20, 2025
What to do if Carrier 38AU Air Conditioner unit operates too long?
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  Jose MooreAug 21, 2025
  If your Carrier Air Conditioner operates too long or continuously, it could be due to several reasons: * Low refrigerant charge: Add refrigerant. * Control contacts fused: Replace the control. * Air in the system: Purge and evacuate the system. * Partially plugged expansion valve or filter drier: Clean or replace them.
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Sherry RobertsAug 27, 2025
Why is my Carrier 38AU Air Conditioner system noisy?
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  erin07Aug 28, 2025
  If your Carrier Air Conditioner system is noisy, it may be due to: Piping vibration, which can be resolved by supporting the piping as required; or a noisy compressor, which may need replacing if the bearings are worn.
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Larry BrennanSep 3, 2025
What causes a hot liquid line in Carrier 38AU Air Conditioner?
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  Andrew FieldsSep 3, 2025
  A hot liquid line in your Carrier Air Conditioner can be caused by: * A shortage of refrigerant due to a leak: Repair the leak and recharge the system. * An expansion valve that opens too wide: Adjust the expansion valve.
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Lacey AustinSep 6, 2025
What causes a frosted liquid line on Carrier Air Conditioner?
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  James SullivanSep 6, 2025
  A frosted liquid line on your Carrier Air Conditioner may be due to: * A restricted filter drier: Remove the restriction or replace the drier. * A liquid line solenoid valve that is partially closed: Replace the valve.
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Thomas HoodSep 10, 2025
Why is my Carrier 38AU Air Conditioner compressor losing oil?
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  Michael BlackwellSep 10, 2025
  Your Carrier Air Conditioner compressor might be losing oil due to: * A leak in the system: Repair the leak. * Crankcase heaters not energized during shutdown: Check wiring and relays, and replace the heater if defective. * Improper interconnecting piping design: Check the piping for oil return and replace if necessary.
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Kimberly TorresNov 16, 2025
Why is my Carrier Air Conditioner compressor not running?
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  gallowaypatriciaNov 16, 2025
  If the compressor of your Carrier Air Conditioner isn't running, it might be due to an open contactor. To resolve this: * Restore power. * Replace the fuse with the correct size after identifying and fixing the cause. * Check the control transformer primary connections and circuit breaker. * Verify the thermostat setting. * Reset the lockout circuit. * Check for refrigerant undercharge or obstructions in indoor airflow. Ensure the liquid line solenoid valve(s) is open. * Check for refrigerant overcharge, obstructions in outdoor airflow, or air in the system. Ensure outdoor fans are operating correctly. * Check for an open condition and allow for reset. Replace if defective. * Tighten all connections. If the contactor is closed, check the connections, look for a blown fu...
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Thomas JonesNov 23, 2025
What to do if Carrier 38AU compressor stops on high-pressure switch?
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  Timothy McleanNov 23, 2025
  If the compressor on your Carrier Air Conditioner stops due to the high-pressure switch, consider these potential causes and solutions: * **Outdoor Fan On:** * Faulty high-pressure switch: Replace the switch. * Reversed fan rotation: Confirm and correct the rotation if necessary. * Restricted airflow: Remove any obstructions. * Air recirculating: Clear the airflow area. * Noncondensables in the system: Recover refrigerant and recharge as required. * Refrigerant overcharge: Recover refrigerant as needed. * Incorrect line voltage: Consult the power company. * Refrigerant system restrictions: Check or replace the filter drier, expansion valve, etc. * **Outdoor Fan Off:** * Fan slips on shaft: Tighten the fan hub setscrews. * Mot...
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Mr. Matthew Larson MDDec 1, 2025
Why does my Carrier 38AU compressor cycle on low-pressure switch?
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  Samuel RiceDec 1, 2025
  If your Carrier Air Conditioner compressor cycles on the low-pressure switch, here are some potential causes and solutions: * **Indoor-Air Fan Running:** * Liquid line solenoid valve(s) fails to open: Check the liquid line solenoid valve(s) for proper operation and replace if necessary. * Filter drier plugged: Replace the filter drier. * Expansion valve power head defective: Replace the power head. * Low refrigerant charge: Add charge and check the low-pressure switch setting. * **Indoor-Air Fan Stopped:** * Electrical connections loose: Tighten all connections. * Fan relay defective: Replace the relay. * Motor overload open: Power supply. * Motor defective: Replace the motor. * Fan belt broken or slipping: Replace or tighten the b...