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Heat pumps · Error codes · Samsung
E604Samsung

E604 on a Samsung heat pump: Communication tracking error between the Hydro Unit and AI Home

Short answer

On a Samsung heat pump, E604 means: Communication tracking error between the Hydro Unit and AI Home. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause. The wording differs by model range — each is shown below.

Reviewed 23 September 2026 · 4 sources

What it means

On the EHS Mono R290 (AE***CXYD*K and pump-integrated AE***CXYB*K)

The manual says: Communication tracking error between the Hydro Unit and AI Home.

Part involved: Wired remote controller / AI Home controller.

When it shows: Unit self-diagnosis: Communication tracking error between the Hydro Unit and AI Home.

Likely causes:

  • Wired remote controller communication, setting, sensor or memory fault; controller wiring (F3/F4) fault.
  • Engineer checks per Samsung service manual: Follow Samsung service manual troubleshooting for this code.

On the EHS Mono R32 (AE***RXYD*G)

The manual says: Communication tracking error between the CONTROL KIT and wired remote controller.

Part involved: Wired remote controller / AI Home controller.

When it shows: Unit self-diagnosis: Communication tracking error between the CONTROL KIT and wired remote controller.

Likely causes:

  • Wired remote controller communication, setting, sensor or memory fault; controller wiring (F3/F4) fault.
  • Engineer checks per Samsung service manual: Follow Samsung service manual troubleshooting for this code.

On the EHS Mono (RC***MHX*A, R410A)

The manual says: Communication tracking error between the CONTROL KIT and.

Part involved: Wired remote controller / AI Home controller.

When it shows: Unit self-diagnosis: Communication tracking error between the CONTROL KIT and.

Likely causes:

  • Wired remote controller communication, setting, sensor or memory fault; controller wiring (F3/F4) fault.
  • Engineer checks per Samsung service manual: Follow Samsung service manual troubleshooting for this code.

On the EHS Split R32 (AE***RXED*G)

The manual says: Communication tracking error between the Hydro Unit and wired remote controller.

Part involved: Wired remote controller / AI Home controller.

When it shows: Unit self-diagnosis: Communication tracking error between the Hydro Unit and wired remote controller.

Likely causes:

  • Wired remote controller communication, setting, sensor or memory fault; controller wiring (F3/F4) fault.
  • Engineer checks per Samsung service manual: Follow Samsung service manual troubleshooting for this code.

Is it safe?

Does the heat pump stop?Yes
Engineer needed?Yes

The heat pump stops until the fault clears or is reset.

Resetting itself: unknown.

Manual reset: unknown.

What you can check

  • Note the full error code shown on the controller; check the heat pump breaker/isolator in the consumer unit is ON; check thermostat/timer and controller operating-mode settings; then contact your installer or Samsung service; Samsung manuals do not describe a homeowner reset for this code.

What the engineer will check

  • Follow Samsung service manual troubleshooting for this code. Any work inside casings, on PCBs, wiring, sensors, pumps, valves or refrigerant is engineer-only.

Who to ask for: Heat pump engineer (controls).

Certification: Competent electrical worker (BS 7671).

What you might notice

What owners and engineers report

9 owner and engineer reports mention this.

  • Controller / thermostat problem on the EHS Mono R290 (AE***CXYD*K and pump-integrated AE***CXYB*K): 2 reports
  • Controller / thermostat problem on the EHS Mono R32 (AE***RXYD*G): 7 reports

Sources

A code explains what the controller detected, not a confirmed root cause.

Reviewed: 23 September 2026