Johnson & Starley 44 Fault Code: Causes, Fixes & Repair Costs
What does the Johnson & Starley 44 fault code mean?
Code 44 on a Johnson & Starley unit indicates a central-heating return sensor error — the return-side temperature probe has gone open or short circuit. On models that combine warm-air heating with a water circuit (WarmCair D/DW variants providing hot water, and Aquair heat interface units), the controller relies on the CH return probe to manage the water side safely; when its circuit fails in either direction, code 44 appears and normal operation is restricted. Diagnosis is the standard sensor routine: inspect the wiring and connectors, measure the sensor's resistance against the specification table, and replace the failed element.
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
- Failed return sensor (open or short) Common
The probe's element fails either open (no reading) or short (impossible reading); both trigger code 44 and both are confirmed by a resistance check.
- Wiring or connector fault Sometimes
Damaged leads or corroded connectors replicate either failure mode; the loom is inspected before the sensor is condemned.
- Board input fault Rare
Rarely the measuring input itself fails; suspected only when a known-good sensor still reads wrongly at the board.
How to fix it
- Reset once and observe DIY safe
Use the reset control (or switch off at the fused spur for 30 seconds and back on) a single time. If the code returns, stop resetting — Johnson & Starley's warm-air units lock out for a reason, and repetition only masks the fault.
- Have a Gas Safe registered engineer complete the documented checks Gas Safe engineer
The engineer will inspect the CH return sensor's wiring, measure its resistance hot and cold against the table, and replace the sensor or repair the circuit as found, then verify flow/return readings track correctly through a heating cycle.
Parts you may need
- CH return sensor (NTC) · from £25
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 £90–£240, depending on the underlying cause.
Frequently asked questions
What does code 44 mean?
The central-heating return temperature sensor circuit has failed — open or short. The unit restricts operation because it manages the water circuit by that reading. An engineer confirms sensor versus wiring with a resistance check and replaces the failed part; it is one of the cheaper repairs.
My unit is warm-air only — why a CH code?
Code 44 belongs to the water side, so it appears on the combined models (WarmCair D/DW with hot water, Aquair heat interface units). If a warm-air-only unit shows it, quote the model to the engineer — sensor channel mapping varies across the range.
How much does it cost?
Typically £90–£240 including the visit — the sensor itself is inexpensive. Regional labour rates vary; get a written quote.