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Error code reference

Goodman Air Conditioner Error Code C4

Indoor Coil froze up.

Goodman codesGoodman air conditioner codes

Indoor Coil froze 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 C4 means on a Goodman air conditioner

Error code C4 on a Goodman air conditioner indicates that the indoor evaporator coil has frozen over. This occurs when the coil's surface temperature drops below 32 degrees Fahrenheit, causing moisture in the air to freeze onto the coil fins and tubing. When ice accumulates, airflow through the coil is progressively blocked, which compounds the problem and can eventually lead to complete airflow restriction and potential compressor damage if left unaddressed.

The most common trigger for coil freeze-up is restricted airflow across the evaporator. A clogged air filter is the leading culprit, as it starves the coil of the warm return air needed to keep the refrigerant from getting too cold. A malfunctioning blower motor or indoor fan can produce the same result. Without adequate airflow, the refrigerant absorbs heat too slowly and the coil drops to freezing temperatures.

Refrigerant issues are the other major category of causes. Low refrigerant charge, whether from a leak or improper servicing, causes the evaporator pressure to drop below its normal operating range. This drops the coil temperature well below the freezing point of water. A restricted capillary tube or metering device can produce a similar effect by causing a pressure drop on the evaporator side. Diagnosing between airflow and refrigerant causes requires checking filter condition, confirming blower operation, and measuring system pressures.

Source: manufacturer service documentation.

Common causes of C4

  1. 01

    Clogged or Dirty Air Filter

    Part replacement

    A blocked filter restricts airflow over the evaporator coil, preventing the refrigerant from absorbing enough heat and causing the coil to freeze. Check the filter visually and replace it if it is heavily loaded with dust or debris.

  2. 02

    Blower Motor or Indoor Fan Failure

    Part replacement

    If the blower motor is running at reduced speed or has stopped entirely, airflow across the evaporator coil drops sharply and freeze-up follows. Confirm the fan is spinning at the correct speed and check for any unusual noises or electrical faults at the motor.

  3. 03

    Low Refrigerant Charge from a Leak

    Part replacement

    A refrigerant leak reduces system pressure on the evaporator side, causing the coil temperature to fall below freezing. This requires leak detection, repair of the leak point, and recharging the system to the correct specification.

  4. 04

    Restricted Capillary Tube or Metering Device

    Part replacement

    A partial blockage in the capillary tube causes a larger than normal pressure drop into the evaporator, sending refrigerant in at too low a pressure and temperature. This condition mimics low refrigerant charge and requires inspection of the metering device.

  5. 05

    Dirty Evaporator Coil

    Wiring / connection

    Heavy buildup of dirt and debris on the coil fins reduces heat transfer and airflow even when the filter is clean. Inspect the coil surface directly and clean it with an appropriate coil cleaner if fouling is present.

See the test procedure for each cause

Frequently asked questions about C4

What does C4 mean on a Goodman air_conditioner?
Code C4 means the indoor evaporator coil has frozen over. Ice has built up on the coil, blocking airflow and preventing the system from cooling properly. The primary causes are a dirty air filter, a blower or fan problem, low refrigerant, or a restricted capillary tube. The system should be turned off to allow the ice to thaw before any diagnostic work begins.
How do I fix a C4 error on my Goodman air conditioner?
Start by turning the system off and switching the fan to the on position to help thaw the coil. Once thawed, check and replace the air filter if it is dirty, and confirm the indoor blower fan is operating correctly. If those checks pass, a licensed HVAC technician should check system refrigerant pressure and inspect the capillary tube for restriction, as both require specialized tools and refrigerant handling certifications.
Is it safe to run my Goodman air conditioner when the C4 code is showing?
No, you should not continue running the system while the coil is frozen. Operating the unit with a frozen coil forces the compressor to work under abnormal conditions, which can cause compressor overheating or failure. Turn the system off immediately and allow it to fully thaw before attempting to restart or diagnose it.
Will resetting my Goodman air conditioner clear the C4 code?
Resetting the unit may clear the code temporarily, but the code will return if the underlying cause is not corrected. A dirty filter, fan failure, refrigerant leak, or restricted capillary tube will continue to cause the coil to freeze regardless of resets. Address the root cause before restarting the system to avoid compressor damage.
How much does it cost to repair a Goodman air conditioner showing a C4 error?
Repair costs vary widely depending on the cause. Replacing an air filter is a low-cost fix in the range of a few dollars to around $30. A blower motor replacement can run from $150 to $450 or more depending on the motor and labor. Refrigerant leak repair and recharge typically falls in the range of $200 to $600 or higher depending on the severity of the leak and the refrigerant type required.

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