Error C And Burner Light

Safety precautions:

1) If you smell gas or suspect a leak, get everyone out of the property, do not operate electrical switches, and call your gas emergency number immediately.

2) Turn off the boiler at the mains switch if instructed in an emergency. Do not open the boiler casing or attempt gas or electrical repairs unless you are a registered gas engineer.

3) Take normal electrical safety care when operating external controls; do not touch internal components.

Initial checks a homeowner can safely do:

1) Check the boiler mode knob is in the correct position (BOILER ON or the mode you require). The manual shows how to select CH, DHW or OFF.

2) Confirm the programmer/timer is set and calling for heat at the times you expect, and that the room thermostat and hot water cylinder thermostat are set above room temperature so they will call for heat.

3) Look at the boiler display: "00" means standby. "C" with the burner light means the boiler is firing to meet demand. If the burner indicator is lit and radiators/hot water are heating, this is normal.

4) Check the boiler pressure gauge is in the normal range (around 1.0–1.5 bar cold for many systems). If pressure is very low, heating may be affected.

5) Listen for the circulation pump running when the boiler is firing; check a few radiators to see if they are warming after a few minutes.

Basic diagnostic and simple fixes you can try:

1) If the boiler is running but you have no hot water or radiators heating, confirm the programmer zone/selector is actually calling for that circuit and that TRVs or radiator valves are open. If the pump is silent, try lifting the pump overrun by turning the mode to ON and listening again; do not dismantle the pump yourself.

2) If the boiler is firing unexpectedly (no timer/thermostat call), check the programmer and any external controls for a stuck or incorrectly set output; temporarily set the programmer to OFF for the CH or DHW circuit to see if the boiler stops.

3) If the boiler shows "C" but nothing warms, check system pressure and bleed any cold radiators to remove air which can prevent flow. Re-pressurise the system using the external filling loop only if you know how; stop filling at the correct pressure and follow your boiler manual.

4) If the burner tries to light and fails intermittently, check other gas appliances in the house to confirm gas supply. Check that any prepayment meter has credit. If other appliances are also dead, the gas supply may be the cause.

5) If the boiler display changes to a different error (for example L2, F3, F1, or E codes) follow the manual guidance for that code; many of those require an engineer.

When to call a professional:

1) Call a Gas Safe registered engineer if the boiler will not stop running when it should, runs continuously without delivering heat, locks out, or if any fault codes other than the normal operation codes are displayed.

2) Any internal component faults (fan, PCB, gas valve, flame detection, sensors, condensate blockages, thermal fuses, pump replacements) must be handled by a qualified engineer. Also call an engineer if you are unsure how to repressurise the system or if pressure repeatedly drops.

3) If you smell gas, see persistent ignition failures, repeated lockouts, or abnormal noises or leaks, contact a Gas Safe engineer or your gas emergency service immediately.

Summary: "C And Burner Light" usually just means the boiler is correctly supplying heat. Carry out the simple checks above (controls, pressure, radiators) and only call a qualified Gas Safe engineer if the boiler behaves unexpectedly, shows other fault codes, or you cannot restore normal heating/hot water after the basic checks.