Daikin SkyAir

Daikin SkyAir Error Code HC

Troubleshooting guide for the Daikin SkyAir system fault HC.

ACLogics Standardize SkyAir diagnostics See the commercial workflow → Standardize SkyAir diagnostics

What It Means

HC signals a malfunction of the (hot) water temperature thermistor, a sensor used on SkyAir outdoor units configured with hydronic or hot-water-related accessories (such as thermal storage tank options) rather than on standard air-source-only installations.

Possible Causes

  • Disconnected or loose water temperature thermistor connector, open or shorted thermistor element, thermistor immersed improperly or displaced from its sensing well, defective outdoor unit control PCB sensor input circuit, wiring damage from moisture at the hydronic accessory connection.

Not sure which one it is — or if it's none of these? Try ACLogics today.

Disclaimer: This information is for general reference. Error codes can vary by model and production year. Always refer to your machine's specific manual and the information printed on the unit itself.
New to this code? Click to see why this happens

Full Diagnosis

HC signals a malfunction of the (hot) water temperature thermistor, a sensor used on SkyAir outdoor units configured with hydronic or hot-water-related accessories (such as thermal storage tank options) rather than on standard air-source-only installations. Like H9, it's a sensor circuit fault — open, shorted, or disconnected thermistor — but tied to the water-side sensing loop instead of the outdoor air sensor. Units without the water/hydronic accessory installed will not report HC.

All Recorded Causes

Disconnected or loose water temperature thermistor connector, open or shorted thermistor element, thermistor immersed improperly or displaced from its sensing well, defective outdoor unit control PCB sensor input circuit, wiring damage from moisture at the hydronic accessory connection.

Verify Before Replacing Parts

  1. Confirm the exact Daikin model family and skyair context before acting on a generic code description.
  2. Verify the sensor or thermistor reading against the expected range for the current operating condition, keeping in mind that disconnected or loose water temperature thermistor connector, open or shorted thermistor e….
  3. Check the sensor harness and board connection before condemning the sensor itself; on Daikin units this is also where you'd confirm the next candidate on the list.
  4. After the correction, run the system long enough to confirm the skyair fault does not return under normal load.

Diagnosing SkyAir across a fleet?

ACLogics standardizes commercial SkyAir diagnostics across your whole team — consistent steps, less guesswork on every call.

See the commercial workflow →