Johnson & Starley 13 Fault Code: Causes, Fixes & Repair Costs
What does the Johnson & Starley 13 fault code mean?
Fault code 13 (shown as E13 on the display) is a safety lockout that appears across several Johnson & Starley ranges — including the Quantec, Reno, WarmCair, and Economaire. Depending on your specific model, it signals one of two related problems: either the boiler's flue gases have exceeded a safe temperature threshold and the appliance has shut itself down to prevent damage, or the control system has detected a flame sensing or gas pressure failure during operation. In both cases the boiler locks out until the underlying fault is identified and resolved. Because fault code numbering is not consistent across all Johnson & Starley product ranges, you should cross-reference with your own model's manual or contact Johnson & Starley directly on 01604 762881 to confirm the exact meaning for your appliance.
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
- Flame sensing failure or dirty flame sensor Common
The ionisation probe that confirms a flame is present can become coated with deposits over time, or the sensing lead connecting it to the control board can develop a fault — including a short to earth. When the signal is weak or absent, the boiler assumes the flame has failed and locks out. This is one of the most frequently cited causes of E13 on the Quantec and Reno ranges.
- Fan fault or restricted airflow Common
If the combustion fan is running slowly, intermittently, or not at all, combustion products cannot be expelled efficiently. This causes flue gas temperatures to climb and can also prevent the boiler from proving safe air flow, triggering a lockout. Blocked flue terminals or obstructed air intake vents produce the same effect.
- Unstable or low gas supply pressure Sometimes
A drop in gas supply pressure during burner operation — caused by a partly closed gas cock, a failing gas meter regulator, or high network demand — can cause the flame to lift or extinguish intermittently. The control board detects this as a flame sensing error and shuts the boiler down.
- Blocked or restricted flue Sometimes
A partial blockage in the flue system — such as debris, a bird's nest, or a damaged terminal — restricts exhaust gas flow and causes heat to build up within the heat exchanger. The overheat limit responds by cutting the boiler off.
- Compromised heat exchanger Rare
Scaling, sludge, or a crack in the heat exchanger can reduce water flow and cause localised overheating of the flue gases, eventually tripping the overheat protection. This tends to appear on older appliances or systems without adequate water treatment.
- Faulty PCB or limit switch Rare
If the limit switch loses continuity — or the PCB itself is misreading sensor signals — the boiler may log E13 even when combustion is otherwise normal. This is a less common cause but worth investigating once all other components have been ruled out.
How to fix it
- Check your gas supply is on DIY safe
Make sure the gas isolation valve on the supply pipe to the boiler is fully open and that other gas appliances in the property (such as a hob or gas fire) are working normally. If no gas appliances are working, contact your gas supplier rather than an engineer.
- Reset the boiler — no more than twice DIY safe
Press and hold the reset button as described in your user manual. If E13 clears and the boiler fires up normally, monitor it over the next hour. If the fault returns after one or two resets, stop resetting — repeated lockouts indicate an underlying fault that needs professional diagnosis.
- Inspect the flue terminal for obvious blockages DIY safe
Go outside and visually check the flue outlet. Look for visible obstructions such as debris, ice, or a bird's nest near the terminal. Do not attempt to clear internal flue blockages yourself. If the terminal looks clear, report your findings to the engineer.
- Check system pressure (if a sealed system boiler) DIY safe
Glance at the pressure gauge on the boiler. It should read between 1.0 and 1.5 bar when cold. If it is below 0.8 bar, top it up via the filling loop following your user manual instructions. Low pressure alone is unlikely to cause E13 but is worth correcting before the engineer visits.
- Have a Gas Safe engineer inspect the flame sensor and sensing lead Gas Safe engineer
An engineer will remove and clean or replace the ionisation probe and check the entire flame detection lead from the probe to the control board for damage, loose connections, or a short to earth. This is the most common fix for E13 on the Quantec and Reno ranges.
- Have the fan tested and flue system inspected Gas Safe engineer
The engineer will check that the combustion fan reaches its correct operating speed and that the flue system is clear, undamaged, and free from restrictions. A faulty fan will need to be replaced; a blocked flue will be cleared or the terminal replaced.
- Have gas supply pressure verified at the boiler Gas Safe engineer
Using a manometer, the engineer will confirm that gas pressure at the boiler inlet is within the manufacturer's specified range both at rest and under load. If pressure drops during firing, the fault may lie with the meter regulator or gas valve, which will need further investigation.
- Have the limit switch continuity and heat exchanger condition checked Gas Safe engineer
The engineer will test the overheat limit switch for correct continuity and inspect the heat exchanger for scaling, sludge build-up, or physical damage. A failed limit switch can be replaced; a severely scaled or cracked heat exchanger may require replacement.
- Have the PCB assessed if all other components test satisfactory Gas Safe engineer
If every other component checks out, the engineer may suspect the PCB is misinterpreting sensor signals. PCB diagnosis and replacement must be carried out by a qualified engineer using manufacturer-compatible parts.
- Call a Gas Safe registered engineer if you have not already done so Gas Safe engineer
E13 is a safety lockout involving gas combustion components. If the boiler has not cleared after one or two resets, book a Gas Safe registered engineer as soon as possible. You can find one at the Gas Safe Register website (gassaferegister.co.uk). Always ask to see their Gas Safe ID card before work begins.
Parts you may need
- Ionisation / flame sensing probe · from £25
- Flame sensing lead and connector · from £20
- Combustion fan (ACF) · from £95
- Overheat limit switch / thermostat · from £30
- PCB (printed circuit board) · from £220
- Flue terminal and cowl assembly · from £35
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 £120–£380, depending on the underlying cause.
Frequently asked questions
Is the E13 fault code the same on all Johnson & Starley boilers?
Not necessarily. Johnson & Starley produce several different product ranges — Quantec, Reno, WarmCair, and Economaire — and the fault code numbering is not universal. On the Quantec and Reno series E13 most commonly relates to flame sensing errors and gas pressure issues, while on other models the same code can indicate a flue or exhaust overtemperature condition. Always check your specific model's manual. If you are unsure, Johnson & Starley's technical line is 01604 762881.
Can I fix Johnson & Starley fault code 13 myself?
There are a couple of quick checks you can safely carry out: confirm the gas supply is on, look for an obvious blockage at the flue terminal outside, and try resetting the boiler once or twice. Beyond that, E13 involves gas combustion components — the flame sensor, gas valve, fan, and potentially the PCB — which must only be worked on by a Gas Safe registered engineer. Attempting to repair these yourself is unsafe and illegal.
How much will it cost to fix E13 on my Johnson & Starley boiler?
Most people pay in the region of £120 to £380 all in, depending on what needs replacing. A flame sensor clean or lead replacement sits at the lower end; a fan replacement typically runs £180–£280 including labour. If the PCB or heat exchanger turns out to be the root cause, costs can be considerably higher — PCBs alone can reach £300–£450 supplied and fitted, and a heat exchanger replacement may exceed that. Getting a fixed-price quote before work starts is always advisable.
Why does my Johnson & Starley boiler keep coming back with fault code 13 after I reset it?
If E13 returns after one or two resets, the underlying fault has not gone away — the boiler is simply locking out again each time it tries to fire and detects the same problem. Repeatedly resetting without fixing the root cause will not resolve it and could mask a developing safety issue. Book a Gas Safe engineer to carry out a proper diagnosis rather than continuing to reset.