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Error code reference

Frigidaire Air Conditioner Error Code HS

Heat thermistor sensor has failed (heat capable models only).

Frigidaire codesFrigidaire air conditioner codes

Heat thermistor sensor has failed (heat capable models only).

First step from the service manual

Check/replace the heat thermistor.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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  • Wiring diagram references and connector pinouts from the OEM service manual
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What HS means on a Frigidaire air conditioner

The HS error code indicates the control board has detected a failure in the heat thermistor sensor, which monitors temperature during heating operation. This sensor is a negative temperature coefficient (NTC) resistor that sends a resistance-based signal to the control board. When the board reads a signal that is out of the expected range, either an open circuit, a short, or a resistance value that does not correspond to any valid temperature, it locks out heating operation and displays HS. This code only appears on heat-capable models, such as heat pump or electric resistance heating units.

In plain terms, your air conditioner has a small sensor that tells the unit how hot or cold the air is during heating mode. That sensor has either failed internally, lost its connection to the control board, or been damaged. Without a reliable reading from this sensor, the unit cannot safely regulate heating output, so it shuts the heating function down to prevent overheating or incorrect operation.

The cooling function may still operate depending on the model, but heating will be disabled until the thermistor is tested and replaced if necessary. Diagnosing this code requires checking the thermistor's resistance with a multimeter and inspecting the wiring harness between the sensor and the control board.

Source: manufacturer service documentation.

Common causes of HS

  1. 01

    Failed heat thermistor

    Part replacement

    The thermistor itself has failed internally, producing a resistance reading outside the control board's accepted range. This is the most common cause and requires replacing the sensor.

  2. 02

    Damaged or disconnected wiring harness to heat thermistor

    Wiring / connection

    The wiring between the thermistor and the control board may have a broken wire, corroded connector, or loose terminal, causing an open circuit or intermittent signal loss.

  3. 03

    Thermistor connector corrosion

    Wiring / connection

    Moisture intrusion can corrode the thermistor connector pins, increasing resistance at the connection point and causing the control board to read an invalid signal even if the thermistor itself is still functional.

  4. 04

    Faulty control board

    Part replacement

    If the thermistor and all wiring test within spec but the HS code persists, the control board's thermistor input circuit may have failed and the board will need replacement.

See the test procedure for each cause

Frequently asked questions about HS

What does the HS error code mean on a Frigidaire air conditioner?
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.
How do I fix the HS error code on a Frigidaire air conditioner?
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.
Can I still use my Frigidaire air conditioner when it shows the HS code?
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.
How much does it cost to fix the HS error code on a Frigidaire AC?
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.
How do I test the heat thermistor to confirm it caused the HS code?
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.

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