Johnson & Starley 57 Fault Code: Causes, Fixes & Repair Costs
What does the Johnson & Starley 57 fault code mean?
Fault code 57 on Johnson & Starley Warmcair warm air boilers indicates that the control system has detected the return airflow temperature is too high. In a healthy warm air system, heated air is distributed around the home and cooler air is drawn back to the unit for reheating. When this circulation is restricted — by a blocked filter, obstructed grille, or a failing fan — warm air gets recycled rather than properly distributed, causing the return air temperature to climb to an unsafe level. The boiler's safety controls then trigger this fault to prevent overheating damage. The manufacturer's own guidance points directly to checking filters and vent grilles as the first port of call.
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
- Blocked or dirty air filter Common
The return air filter is the single most common trigger for this fault. Over time, dust and debris build up on the filter mesh, progressively throttling the airflow back to the unit. Less air means the return temperature climbs quickly, tripping code 57. Filters on warm air units often go unchecked for years, making this the first thing to inspect.
- Obstructed air vents or distribution ducts Common
Furniture pushed against floor or ceiling grilles, objects dropped into floor registers, or collapsed sections of ductwork can all restrict the circulation of warm air around the home. Even a single blocked grille can significantly reduce airflow volume and push return temperatures up.
- Circulation fan fault or failing motor Sometimes
The fan is responsible for moving air through the heat exchanger and around the duct system. If the fan motor windings have deteriorated, the bearings have worn (often accompanied by a screeching noise on start-up or shut-down), or the fan blade has become clogged with debris, airflow drops and return temperatures rise. Replacement motors for older Warmcair units — particularly the common '32' model — can be hard to source, though motor refurbishment is available.
- Heat exchanger or fan chamber build-up Sometimes
A layer of dust or debris on the heat exchanger surfaces or inside the fan chamber reduces the efficiency of heat transfer and restricts airflow through the unit. This tends to develop gradually on boilers that have missed annual services.
- Loose or corroded electrical connections to the fan Rare
Vibration from the fan motor can gradually work connections loose on the wiring loom between the fan and the PCB. When the PCB receives inconsistent or absent signals from the fan, it may misread the airflow situation and trigger a lockout or fault code even if the fan itself is mechanically sound.
- PCB fault sending incorrect fan signals Rare
In less common cases the printed circuit board itself develops a fault, causing it to misinterpret sensor readings or send incorrect commands to the fan. This can produce spurious fault codes that persist even after filters and ducts have been cleared.
How to fix it
- Check that all room air grilles and return-air vents are unobstructed DIY safe
Walk around the property and confirm that every supply grille and return grille is fully open and not blocked by furniture, rugs, or curtains. Remove any objects that are sitting over floor registers. This costs nothing and takes five minutes.
- Inspect and clean the air filter DIY safe
Locate the return-air filter on your Warmcair unit — typically behind a removable panel near the base or side of the unit. Slide it out and check for a visible build-up of dust and fluff. A lightly soiled filter can be vacuumed clean; a heavily clogged or damaged filter should be replaced. Refer to your boiler's documentation for the correct filter size.
- Check the ductwork for obvious blockages or collapsed sections DIY safe
Inspect any accessible sections of ductwork (usually in a loft, cupboard, or underfloor void) for obvious damage, disconnected joints, or crushing. Do not dismantle sealed sections — just check what is visible.
- Reset the boiler and observe DIY safe
Once you have cleaned the filter and cleared any obstructions, reset the boiler following the manufacturer's instructions (usually a dedicated reset button or switch on the control panel). Allow the boiler to run through a full heating cycle and monitor whether the fault returns. Do not reset more than two or three times in quick succession.
- If the fault persists, call a Gas Safe registered engineer Gas Safe engineer
If cleaning the filter and clearing the grilles does not clear code 57, the fault is likely inside the unit — a failing fan motor, build-up on the heat exchanger, wiring issues, or a PCB problem. All of these require a Gas Safe registered engineer with specific warm air boiler experience. Ask for an engineer familiar with Johnson & Starley Warmcair units, as they are quite different from conventional wet-system boilers.
Parts you may need
- Return air filter (Warmcair) · from £20
- Circulation fan motor (refurbished for Warmcair 32) · from £150
- Circulation fan assembly · from £175
- Fan motor capacitor · from £15
- PCB (control board) · from £280
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 £80–£380, depending on the underlying cause.
Frequently asked questions
Can I fix Johnson & Starley fault code 57 myself?
Partially. Homeowners can safely clean or replace the air filter, unblock grilles, and reset the boiler — and in many cases that is all that is needed. However, if the fault is caused by a failing fan motor, wiring fault, or PCB issue, those repairs must be carried out by a Gas Safe registered engineer. Warm air boilers are specialised appliances; always use an engineer with experience on Johnson & Starley Warmcair units specifically.
Why does my Johnson & Starley Warmcair make a screeching noise before showing fault code 57?
A screeching or grinding noise — particularly on start-up or shut-down — almost always points to worn fan bearings. As the bearings deteriorate, the fan struggles to reach or maintain the correct speed, airflow drops, and the return air temperature climbs until code 57 is triggered. This is a mechanical failure that needs a Gas Safe engineer to inspect and either refurbish or replace the fan motor.
How much does it cost to fix fault code 57 on a Warmcair boiler?
If the cause is simply a dirty filter — which it often is — the cost may be as little as £80–£100 for a service call including filter replacement. A fan motor refurbishment or replacement typically adds up to £250–£380 all-in including labour. PCB replacement can cost more (often £300–£500 with labour), and a heat exchanger is rarely economic to replace on an older unit — at that point a full system replacement is usually the better option.
How often should I clean the filter on a Johnson & Starley Warmcair boiler?
Johnson & Starley recommend checking and cleaning the return-air filter at least every three months during the heating season, and replacing it annually or when it can no longer be adequately cleaned. A clogged filter is the leading cause of fault code 57 and is straightforward for a homeowner to manage. Annual professional servicing by a Gas Safe engineer should also include a thorough inspection of the fan, heat exchanger, and ductwork.