E901 on a Samsung heat pump: Water Inlet Sensor Error (open/short)
Short answer
On a Samsung heat pump, E901 means: Water Inlet Sensor Error (open/short). 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 · 3 sources
What it means
On the EHS Mono R290 (AE***CXYD*K and pump-integrated AE***CXYB*K)
The manual says: Water Inlet Sensor Error (open/short).
Part involved: Water Inlet Sensor Error (open/short).
When it shows: Unit self-diagnosis: Water Inlet Sensor Error (open/short).
Likely causes:
- Water-side or tank temperature sensor open/short circuit, detached or mis-configured; connector or PCB fault.
- Engineer checks per Samsung service manual: Check sensor connection status, sensor location and sensor resistance against the Samsung resistance table (103 or 204 type); replace sensor or PCB if required.
On the EHS Mono R32 (AE***RXYD*G)
The manual says: Water inlet (PHE) temperature sensor error(open/short).
Part involved: Water inlet (PHE) temperature sensor error(open/short).
When it shows: Unit self-diagnosis: Water inlet (PHE) temperature sensor error(open/short).
Likely causes:
- Water-side or tank temperature sensor open/short circuit, detached or mis-configured; connector or PCB fault.
- Engineer checks per Samsung service manual: Check sensor connection status, sensor location and sensor resistance against the Samsung resistance table (103 or 204 type); replace sensor or PCB if required.
On the EHS Split Generation 4 (AEX/AEN, 2014)
The manual says: Water inlet temperature sensor error (open/short).
Part involved: Water inlet temperature sensor error (open/short).
When it shows: Unit self-diagnosis: Water inlet temperature sensor error (open/short).
Likely causes:
- Water-side or tank temperature sensor open/short circuit, detached or mis-configured; connector or PCB fault.
- Engineer checks per Samsung service manual: Check sensor connection status, sensor location and sensor resistance against the Samsung resistance table (103 or 204 type); replace sensor or PCB if required.
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; then contact your installer or Samsung service; Samsung manuals do not describe a homeowner reset for this code.
What the engineer will check
- Check sensor connection status, sensor location and sensor resistance against the Samsung resistance table (103 or 204 type); replace sensor or PCB if required. Any work inside casings, on PCBs, wiring, sensors, pumps, valves or refrigerant is engineer-only.
Who to ask for: Heat pump engineer (Samsung-trained).
Certification: Competent electrical worker (BS 7671).
What you might notice
What owners and engineers report
7 owner and engineer reports mention this.
- No heating on the EHS Mono R32 (AE***RXYD*G): 6 reports
- No hot water on the EHS Mono R32 (AE***RXYD*G): 1 report
Sources
- EHS R290 Mono Outdoor Unit Installation Manual AE***CXYD** (EU) DB68-12496A-03 ↗ · DB68-12496A-03 · page p.24 · Reviewed 23 September 2026
- EHS R-32 Mono Outdoor Unit Installation Manual (EU) DB68-08408A-07 ↗ · DB68-08408A-07 · page p.44 · Reviewed 23 September 2026
- Samsung Eco Heating System Service Manual - Outdoor Unit AEX060-160ED*HA / Hydro Unit AEN080/160YD*HA (file RC160MHXGA_SM_E_34513A(1)) ↗ · 34513A(1) · page ManualsLib viewer pp.49, 53 (printed pp.48, 52) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026