Daikin Chiller

Daikin Chiller Error Code H3

Troubleshooting guide for the Daikin Chiller system fault H3.

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What It Means

Reports that the high pressure switch circuit itself has failed open, shorted, or lost continuity — a wiring or hardware fault in the switch or its connector — as distinct from E3 and 73, which log an actual HPS trip caused by genuinely excessive discharge pressure on System No.

Possible Causes

  • Broken or corroded wire at the high pressure switch terminal.
  • Loose or disconnected HPS connector.
  • High pressure switch contacts stuck open or failed internally.
  • Moisture intrusion at the switch housing.
  • Damaged wiring harness between the HPS and the outdoor unit PCB.

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.
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Full Diagnosis

Reports that the high pressure switch circuit itself has failed open, shorted, or lost continuity — a wiring or hardware fault in the switch or its connector — as distinct from E3 and 73, which log an actual HPS trip caused by genuinely excessive discharge pressure on System No. 1 and System No. 2 respectively. Because H3 is a switch-integrity fault rather than a confirmed pressure event, verify actual head pressure before replacing the switch, since a wiring or connector problem can mimic a switch failure. Compressor operation on the affected circuit is locked out until the switch circuit is confirmed sound and the fault is reset.

All Recorded Causes

Broken or corroded wire at the high pressure switch terminal. Loose or disconnected HPS connector. High pressure switch contacts stuck open or failed internally. Moisture intrusion at the switch housing. Damaged wiring harness between the HPS and the outdoor unit PCB. Defective outdoor unit PCB input circuit for the HPS.

Verify Before Replacing Parts

  1. Confirm the exact Daikin model family and chiller context before acting on a generic code description.
  2. Verify airflow first, then confirm operating pressures and temperature relationship before adjusting charge, since broken or corroded wire at the high pressure switch terminal.
  3. Look for restrictions, iced coils, or dirty heat-transfer surfaces that can mimic a charge problem, and separately confirm loose or disconnected HPS connector.
  4. After the correction, run the system long enough to confirm the chiller fault does not return under normal load.

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