Heat pumps · Error codes · Lailey and Coates Ltd
E03Lailey and Coates Ltd · Lailey & Coates LCM monobloc (LCM-06/09/17)
E03 on a Lailey and Coates Ltd Lailey & Coates LCM monobloc: Outdoor unit inverter module communication failure
Short answer
On a Lailey and Coates Ltd heat pump, E03 means: Outdoor unit inverter module communication failure. 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: Outdoor unit inverter module communication failure.
Likely causes:
- Contactor or connection fault between outdoor unit and control box.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
What you can check
- Read and note the code shown on the controller display, then contact your installer or service engineer.
- Check the heat pump's breaker/isolator at the consumer unit is switched on (do not repeatedly reset if it trips).
What the engineer will check
- Check contactors and connections from outdoor unit to control box.
- Check communication cable between controller/PCB/driver board (type, polarity, termination).
- Check power supply to the remote module.
- Replace faulty PCB/controller if wiring is sound.
Who to ask for: heat pump controls / electrical.
Certification: Electrical competence.
What you might notice
Sources
- Lailey & Coates Monobloc Air Source Heat Pumps - Installation & Maintenance Manual (LCM-06 / LCM-09 / LCM-17) ↗ · page 18 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026