Heat pumps · Error codes · ELCO
903ELCO · Aeropur CRX (006/008/012/015) monobloc air-to-water
903 on an ELCO Aeropur CRX monobloc air-to-water: System return sensor damaged
Short answer
On an ELCO heat pump, 903 means: System return sensor damaged. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: System return sensor damaged.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
What you can check
- Note the error code shown and give it to your installer / service engineer.
What the engineer will check
- Check probe wiring/connector and resistance; replace probe.
Who to ask for: heat pump / electrical.
What you might notice
Sources
- AEROPUR Instruction manual (Brugsanvisning, 420010710000 - 12/2015; English section p13-26) ↗ · 420010710000 · page 23 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026