Frigidaire Air Conditioner Error Code HS

The HS code means the control board has detected a failure in the heat thermistor sensor. This sensor monitors temperature during heating operation, and when it sends a signal outside the expected resistance range, the unit disables heating and displays HS. This code only appears on Frigidaire models that include a heating function.

Cooling mode may still function on some models because the heat thermistor is specific to the heating circuit. However, the heating function will be disabled until the fault is resolved. Do not attempt to use heating mode while this code is active, as the control board is blocking it intentionally to prevent unsafe operation.

Disconnect the thermistor from the wiring harness and use a multimeter set to measure resistance (ohms). At room temperature, most NTC thermistors used in window and portable AC units read between 5,000 and 20,000 ohms, but check your specific model's service documentation for the correct value. A reading of zero (short) or infinite resistance (open circuit) confirms a failed thermistor. If the resistance is within spec, inspect the connector and wiring before replacing parts.

Start by unplugging the unit and locating the heat thermistor, which is typically clipped to the evaporator coil or air inlet area. Disconnect it and measure its resistance with a multimeter at room temperature. Compare the reading to the resistance chart in your service manual. If the reading is open, shorted, or far outside the specified range, replace the thermistor. Also inspect the wiring harness and connector for damage or corrosion before assuming the sensor itself is bad.

A replacement heat thermistor is generally an inexpensive part, typically ranging from $10 to $30 depending on the model. If you are comfortable with basic electrical testing using a multimeter and can access the sensor, this is a DIY-friendly repair. If the control board turns out to be the cause, board replacement costs can range from $80 to $200 or more for the part alone, and professional labor will add to that cost.