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Error code reference

Goodman Heat Pump Error Code 01

Low side fault

Goodman codesGoodman heat pump codes

Low side fault - low refrigerant charge, liquid line restriction, indoor blower motor failure, or indoor thermostat set extremely low.

First step from the service manual

Verify refrigerant charge; adjust as needed. Check for restricted liquid line.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What 01 means on a Goodman heat pump

Error code 01 on a Goodman heat pump indicates a low side fault, meaning the suction side pressure of the refrigerant circuit has dropped below acceptable operating limits. The low pressure switch, which monitors suction pressure, has tripped and signaled the control board to shut down the compressor to prevent damage. This condition points to an issue somewhere in the refrigerant circuit or the airflow system that is causing abnormally low evaporator pressure.

The most frequent cause is an insufficient refrigerant charge due to a leak somewhere in the system. When refrigerant mass is low, suction pressure drops, starving the compressor and reducing system efficiency. A restricted liquid line is another direct cause, as a blocked filter drier or kinked line will reduce refrigerant flow into the evaporator, causing suction pressure to collapse even when the charge is correct. Both conditions require gauge manifold measurements to distinguish between them.

Airflow problems on the indoor side can also trigger this fault. If the indoor blower motor has failed or is running at reduced speed, heat transfer at the evaporator decreases and the refrigerant temperature drops excessively, causing the suction pressure to fall. Additionally, if the indoor thermostat is set to an extremely low setpoint, the system may run continuously beyond its capacity, driving suction pressure down to fault levels. Diagnostic work should begin with verifying refrigerant charge using gauge readings, then inspecting the liquid line for restriction before moving to airflow and controls checks.

Source: manufacturer service documentation.

Common causes of 01

  1. 01

    Low refrigerant charge

    Part replacement

    A refrigerant leak causes suction pressure to drop below the low pressure switch threshold. A technician will need to connect a gauge manifold to confirm low suction pressure and locate the leak before recharging the system.

  2. 02

    Liquid line restriction

    Part replacement

    A clogged filter drier or kinked liquid line restricts refrigerant flow into the evaporator coil, collapsing suction pressure even if the refrigerant charge is correct. Abnormally cold temperatures or frost on the liquid line near the restriction are common indicators.

  3. 03

    Indoor blower motor failure

    Part replacement

    If the indoor blower motor has failed or is running below rated speed, insufficient air moves across the evaporator coil, causing refrigerant to over-cool and suction pressure to fall. Check that the blower runs at startup and verify airflow at the supply registers.

  4. 04

    Extremely low thermostat setpoint

    Wiring / connection

    Setting the thermostat to an unusually low temperature causes the system to run beyond its design capacity, driving suction pressure down until the low pressure switch trips. Raising the setpoint to a normal operating temperature may resolve the fault if no other issues are present.

See the test procedure for each cause

Frequently asked questions about 01

What does 01 mean on a Goodman heat_pump?
Error code 01 on a Goodman heat pump indicates a low side fault, meaning the suction pressure in the refrigerant circuit has dropped too low and the low pressure switch has shut the compressor down. Common causes include low refrigerant charge, a restricted liquid line, indoor blower motor failure, or a thermostat set to an extremely low temperature. A technician should connect gauges to confirm suction pressure before proceeding with repairs.
Can I fix a Goodman heat pump error code 01 myself?
Some checks, such as confirming the thermostat setpoint is reasonable and verifying the indoor blower is running, can be done without special tools. However, diagnosing and correcting refrigerant charge or a liquid line restriction requires EPA Section 608 certification and gauge manifold equipment. Most repairs for this code should be handled by a licensed HVAC technician.
Is it safe to keep running my Goodman heat pump when error code 01 appears?
No. Error code 01 causes the system to shut down the compressor specifically to prevent damage from low suction pressure. Attempting to override or repeatedly reset the system without fixing the underlying cause can damage the compressor, which is one of the most expensive components in the system. Leave the unit off until the fault is properly diagnosed and repaired.
Will resetting my Goodman heat pump clear error code 01?
Resetting the unit by cycling power may temporarily clear the fault and allow the system to restart, but if the underlying cause is not corrected, the low pressure switch will trip again and the code will return. A reset does not fix a refrigerant leak, a restricted line, or a failed blower motor. Clearing the code is only useful as part of a diagnostic process after a repair has been made.
How much does it cost to repair a Goodman heat pump showing error code 01?
Repair costs vary significantly depending on the root cause. Refrigerant leak detection and recharging typically ranges from $200 to $600 or more depending on refrigerant type and the amount needed. Replacing a filter drier may cost $150 to $400 in parts and labor. An indoor blower motor replacement can range from $300 to $700. A technician's diagnostic visit is usually an additional $75 to $150 on top of repair costs.

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