Goodman Air Conditioner Error Code F3

The F3 code on a Goodman air conditioner means the Indoor Ambient Thermistor is reading a temperature value outside the valid range of -20°F to 200°F. The control board uses this sensor to monitor indoor air temperature, and when the reading falls outside that range, the system triggers the fault. The thermistor is identified by its black housing and connects to the control board via a low-voltage wiring harness. A failed sensor is the most likely cause.

Operating the unit with an active F3 fault is not recommended. The control board cannot accurately monitor indoor conditions without a valid thermistor reading, which may cause the system to operate incorrectly or prevent it from running at all. Continued operation in this state can potentially mask other developing issues, so the fault should be diagnosed and corrected promptly.

Repair costs depend on what component has failed. If only the Indoor Ambient Thermistor needs replacement, the part itself is generally inexpensive, typically in the range of $10 to $40, and labor for a straightforward thermistor swap is usually on the lower end of a service call charge. If the fault turns out to involve the control board, total repair costs can range from $200 to $600 or more depending on the board and labor rates in your area.

The recommended first step is to replace the black Indoor Ambient Thermistor. Before replacing it, inspect the wiring harness and connector at both the thermistor and the control board for any loose pins, broken wires, or corrosion, since a wiring issue can produce the same fault without the sensor being defective. If the wiring checks out and the fault persists after thermistor replacement, the control board input circuit may need evaluation.

A power reset may temporarily clear the F3 code from the display, but the fault will return if the underlying cause has not been addressed. If the thermistor is failed, open, or shorted, the control board will detect the out-of-range reading again as soon as it checks the sensor input. A lasting repair requires replacing the thermistor or correcting the wiring fault.