Goodman Air Conditioner Error Code C5

The C5 error code on a Goodman air conditioner indicates that the outdoor coil temperature is registering too high relative to the measured outdoor ambient temperature. This condition is monitored by the control board using input from the outdoor coil temperature sensor. Under normal operation, the coil temperature during cooling should remain within an expected range above or below the ambient reading. When the coil temperature exceeds the threshold the control logic expects for the current ambient conditions, the C5 fault is triggered and the unit may lock out to protect the refrigerant circuit and compressor.

The most frequent cause of this fault is restricted airflow across the outdoor condenser coil. A coil clogged with dirt, grass clippings, cottonwood seeds, or other debris reduces the system's ability to reject heat, causing coil temperatures to rise abnormally. Similarly, a failing condenser fan motor or bent/damaged fan blade will reduce airflow volume, producing the same effect. The first diagnostic step is a visual inspection of the coil surface for blockage and a check of the condenser fan for proper operation and correct rotation direction.

Less commonly, C5 can be caused by refrigerant overcharge, a faulty outdoor coil temperature sensor reporting an incorrect reading, or a defective control board misinterpreting a valid sensor signal. If airflow is confirmed to be adequate and the coil is clean, technicians should check the sensor resistance against specifications and verify the refrigerant charge using manifold gauges. Overcharge conditions elevate head pressure and coil temperature and require refrigerant recovery before recharging to the correct weight or pressure specification.