Sime AL 44 Fault Code: Causes, Fixes & Repair Costs
What does the Sime AL 44 fault code mean?
AL 44 on a Sime boiler is a gas valve timeout fault without flame: the control board commanded the gas valve during an ignition attempt but the expected result — a proven flame within the allowed window — never came, in a way that implicates the valve or its control rather than a simple failed light-off. Sime's documented solution is to check the gas valve and board, and to involve the Technical Assistance Centre if needed. On these boilers the valve is an electronically controlled component wired directly into the combustion management system (the SGV valve on combustion-control models), so faults in the valve, its wiring or the board's driver stage all surface through codes like this one.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- Gas valve not responding correctly Common
A failing valve coil or actuator does not open (or modulate) as commanded, so no gas — and no flame — arrives within the timeout. Sime's remedy column names the valve first.
- Valve wiring or connector fault Sometimes
A degraded connector or damaged loom between board and valve interrupts the drive signal. Electrically indistinguishable from a valve fault until measured.
- Board driver stage fault Sometimes
The PCB circuit that drives the valve can fail, commanding nothing despite the logic calling for gas. Sime pairs 'check gas valve and board' for exactly this reason.
- Gas supply interruption Rare
A closed cock or supply problem at the moment of ignition can contribute; engineers verify inlet pressure as a matter of course before condemning parts.
How to fix it
- Check other gas appliances DIY safe
If nothing else in the property lights either, the issue is supply, not the boiler — check your emergency control valve and supplier before booking a repair.
- Reset once with the OK/RESET button DIY safe
Hold the OK RESET button for more than 3 seconds. Sime boilers allow a limited number of consecutive resets (six) before locking out on AL 28, so if the code returns after one or two attempts, stop and book an engineer rather than using them all up.
- Have a Gas Safe registered engineer carry out Sime's documented remedy Gas Safe engineer
The engineer will test the gas valve's coils and operation, inspect its wiring, verify inlet working pressure, and test the board's valve drive — Sime's documented 'check gas valve and board'. On combustion-control models a full self-calibration and flue-gas analysis follows any valve or board replacement.
Parts you may need
- Gas valve (SGV) · from £150
- Control PCB · from £200
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £150–£400, depending on the underlying cause.
Frequently asked questions
What does AL 44 mean on a Sime boiler?
During ignition the board operated the gas valve but never got a proven flame within the allowed time, in a way that points at the valve or its control electronics. Sime's manual says to check the gas valve and board — this is a workshop-level electrical diagnosis, not a reset-and-hope fault.
Is it safe to keep resetting AL 44?
One reset is fine; repeated resets are not. Each attempt operates the gas valve on a fault that involves the valve itself, and Sime boilers lock out after six consecutive resets anyway (AL 28). If it returns, leave it for a Gas Safe registered engineer.
What does the repair cost?
A wiring repair sits at the bottom of the typical £150–£400 range, a replacement gas valve in the middle, and a control board at the top — plus recommissioning with self-calibration on combustion-control models. Regional prices vary; get a written quote.