BoilerFaultCodesSime AL 04 Fault Code
Also written as AL04 — same fault.
The Sime AL 04 fault code means: your boiler's hot water sensor has failed or has a bad connection, which means the system cannot correctly measure the temperature of the water coming out of your taps.. It appears on 13 Sime models in our database.
Technical description: Domestic hot water sensor (SS) fault — combi models; check wiring connections; replace sensor if open/short circuit
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Sime models that show the AL 04 fault code
Click a model for the full fault code list and model-specific repair notes.
- Brava One HE Repair: £90-160
- Dewy 30/130 HE FS Repair: £90-160
- Dewy 30/50 HE WM Repair: £90-160
- Giulia Combi 30 Repair: £90-160
- Halstead Trio Repair: £90-160
- Metropolis DGT 25 BF Repair: £90-160
- Mia 30 Repair: £90-160
- Murelle One HE Repair: £90-160
- Murelle Pro HE 25 HO Repair: £90-160
- Murelle Pro HE Combi Repair: £90-£160
- Murelle Pro HE MkII Combi Repair: £90-160
- Murelle Pro HE R MkII System Repair: £100-180
- Murelle Pro HE System R Repair: £90-160
Source
Sime AL 04 fault code information on this page is sourced and cross-checked against the official Sime service / installation manuals for each affected model.
- Sime Brava One HE manual (PDF)
- Sime Dewy 30/130 HE FS manual (PDF)
- Sime Dewy 30/50 HE WM manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026