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Error code reference

Goodman Air Conditioner Error Code C1

Indoor Coil is freezing up.

Goodman codesGoodman air conditioner codes

Indoor Coil is freezing up.

First step from the service manual

Clean filter, Check for fan and blower operation, Check for Refrigerant loss or Restricted capillary tube.

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

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What C1 means on a Goodman air conditioner

The C1 error code on a Goodman air conditioner indicates that the indoor evaporator coil is freezing up. This occurs when the coil's surface temperature drops below 32°F and moisture in the air passing over it begins to form ice rather than condensate. When ice accumulates on the coil, it progressively restricts airflow, which compounds the problem and can eventually cause a complete blockage of air movement through the air handler. If left unaddressed, a frozen coil can cause liquid refrigerant to migrate back to the compressor, potentially causing compressor damage.

The most common trigger for coil freeze-up is restricted airflow across the evaporator. A dirty or clogged air filter reduces the volume of warm return air passing over the coil, which prevents the refrigerant inside from absorbing enough heat to stay above freezing. Similarly, a failed or underperforming blower motor will produce the same result. In both cases, the refrigerant remains too cold relative to the airflow it receives, and ice begins to form on the coil fins and tubing.

Refrigerant-side issues are another major cause of this condition. Low refrigerant charge due to a leak causes the remaining refrigerant to expand more aggressively in the evaporator, dropping coil temperatures well below normal operating range. A restricted capillary tube or metering device creates a similar pressure drop effect, causing abnormally low evaporator pressure and suction line temperatures. Diagnosing between these causes requires checking filter condition and blower operation first, then moving to refrigerant pressure measurements if airflow components check out normally.

Source: manufacturer service documentation.

Common causes of C1

  1. 01

    Dirty or Clogged Air Filter

    Part replacement

    A heavily restricted filter reduces warm return airflow across the evaporator coil, causing refrigerant temperatures to drop below freezing. Inspect the filter and replace it if it is visibly dirty or has not been changed within the recommended interval.

  2. 02

    Blower Motor or Fan Failure

    Part replacement

    If the indoor blower motor is not operating or is running below its rated speed, insufficient air moves across the coil and freezing occurs even with a clean filter. Check that the blower energizes on a call for cooling and verify it reaches full operating speed.

  3. 03

    Low Refrigerant Charge Due to a Leak

    Part replacement

    A refrigerant leak lowers system pressure, causing the evaporator to operate at abnormally low temperatures and freeze the coil. This requires a licensed technician to locate the leak, perform repairs, and recharge the system to the correct specification.

  4. 04

    Restricted Capillary Tube or Metering Device

    Part replacement

    A blockage or restriction in the capillary tube causes excessive pressure drop entering the evaporator, driving coil temperatures dangerously low and producing ice buildup. This is diagnosed by measuring suction pressure and comparing it against expected operating pressures for the system.

  5. 05

    Blocked or Closed Supply Registers

    Wiring / connection

    Closed, blocked, or undersized supply registers reduce total system airflow and can contribute to coil freeze-up even when the filter and blower are functioning correctly. Check that all supply and return registers in the home are fully open and unobstructed.

See the test procedure for each cause

Frequently asked questions about C1

What does C1 mean on a Goodman air_conditioner?
The C1 code on a Goodman air conditioner means the indoor evaporator coil is freezing up. Ice formation on the coil restricts airflow and prevents the system from cooling effectively. The most common causes are a clogged air filter, a blower that is not operating correctly, low refrigerant due to a leak, or a restricted capillary tube.
How do I fix a C1 error on my Goodman air conditioner?
Start by turning the system off and allowing the coil to thaw completely, which can take several hours. Then replace the air filter if it is dirty and confirm the indoor blower fan is running properly when the unit is powered on. If the error returns after these steps, a technician will need to check refrigerant pressure and inspect the capillary tube for restrictions or evidence of a refrigerant leak.
Is it safe to keep running my Goodman AC when it shows a C1 code?
Continuing to run the system with a frozen coil is not recommended. Ice buildup progressively blocks airflow and can force liquid refrigerant back into the compressor, which can cause serious and expensive compressor damage. Turn the system off and let it thaw before attempting any diagnosis or restarting the unit.
Will resetting my Goodman air conditioner clear the C1 error?
Resetting the unit may temporarily clear the code, but if the underlying cause is not corrected the coil will freeze again and C1 will return. A reset is only useful as a first step after you have already addressed the root cause, such as replacing the filter or confirming blower operation. Persistent C1 codes after a reset indicate a refrigerant or mechanical issue that requires professional diagnosis.
How much does it cost to repair a Goodman air conditioner showing a C1 code?
Costs vary widely depending on the root cause. Replacing an air filter is a low-cost fix in the range of a few dollars to around $30. Blower motor replacement typically runs in the range of $150 to $600 or more including labor. Refrigerant leak repair and recharge can range from $200 to $1,500 or higher depending on the location of the leak, refrigerant type, and labor rates in your area.

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