Goodman Air Conditioner Error Code F4

The F4 code means the indoor coil thermistor has reported a temperature reading that is either too high or too low compared to the system's accepted operating tolerances. The indoor coil thermistor, identified by its red leads, monitors the evaporator coil temperature and sends that data to the control board. When the signal falls out of range, the control board logs F4 to alert the technician. The first recommended step is to replace the red indoor coil thermistor.

Running the system while F4 is active is not recommended. The control board relies on accurate coil temperature data from the thermistor to manage system operation and protection functions. Without a reliable temperature reading, the unit may operate improperly, potentially leading to issues like coil icing or insufficient compressor protection. It is best to address the fault before continuing normal operation.

A power reset may temporarily clear the F4 code, but if the underlying thermistor problem is still present, the fault will return once the system runs through its diagnostics again. Resetting without addressing the faulty thermistor or wiring is not a lasting solution. The root cause needs to be identified and corrected to prevent the code from recurring.

A knowledgeable DIYer can inspect the thermistor for physical damage, check that it is properly seated in its mounting clip on the coil, and examine the wiring connector for corrosion. Replacing the thermistor itself is a relatively straightforward task if you are comfortable working inside the air handler. However, if the fault persists after thermistor replacement, diagnosing the control board or wiring requires more advanced skills and a multimeter.

If only the indoor coil thermistor needs replacement, the repair is typically among the more affordable fixes, with parts costs generally ranging from around $10 to $50 and labor costs varying by region and technician. If the fault turns out to involve the control board, repair costs can range considerably higher, from $150 to $600 or more depending on parts and labor. Getting a diagnostic visit from a qualified technician will give you a clearer cost estimate for your specific situation.