Error E13

Safety precautions:

- If you are not Gas Safe registered or competent with boiler electrics, stop at the homeowner checks and call a Gas Safe engineer. Do not open gas or sealed boiler components.

- Before any visual inspection switch off the boiler at the front panel and at the electrical isolator (mains), and isolate water supply if you need to remove pipework or fittings.

- Do not repeatedly reset a locked-out boiler; one or two resets to test are acceptable but repeated resets can be unsafe and may mask a persistent fault.

Initial checks a homeowner can do (safe, non-intrusive):

1. Note whether the boiler is locked out and whether E13 is displayed continuously after a reset.

2. Try a single reset: follow the Baxi reset procedure (hold reset for 3–5 seconds) and see if the fault clears. Do not cycle repeatedly.

3. Check central heating pressure on the gauge (normally around 1–1.5 bar when cold). If pressure is very low (<0.5 bar) other faults can appear; top up via the filling loop if you are comfortable doing so and the boiler manual allows it.

4. Confirm the CH pump appears to run when demands are made (heat on). You may hear or feel the pump come on. Also check motorised valves/room thermostat settings to ensure a demand is actually present.

5. Look for obvious signs of leaks, corrosion or water near the boiler base or pipework which could have affected the flow switch or wiring.

Specific diagnostic and fix steps (for a qualified person / engineer):

1. Locate the differential flow switch (consult boiler schematic/manual). On many combi units it is a small paddle or reed-type switch in the primary flow pipe or inside the hydraulic block.

2. With the boiler powered off and isolated, visually inspect the switch and its wiring for corrosion, water ingress, loose connectors or damage. Repair/replace damaged connectors or pigtails as required.

3. With safe isolation procedures followed, use a multimeter to check continuity of the flow switch and observe its state with no pump demand and then with the pump running (or with the boiler calling for heat). The switch should change state (open/close) when flow starts/stops. E13 indicates it remains closed when it should open.

4. If the switch is mechanically stuck or contaminated, removing the switch or paddle and cleaning may restore operation. Replace the switch if mechanical cleaning does not free it or if electrical tests show a fail.

5. Check for wiring short circuits to 0V or live that could force the input to read as closed; trace the cable back to the PCB and inspect for chafing or pinched sections.

6. Verify pump operation and three-port diverter valve operation. If the pump runs continuously or a valve forces continuous bypass flow, the flow switch may be seeing continuous movement. Correct pump wiring or replace faulty valves as needed.

7. If wiring and switch test correctly, but the PCB still registers E13, check the PCB input for the flow switch for fault or replace the PCB if proven defective by a qualified engineer.

When to call a professional:

- Call a Gas Safe registered engineer if you cannot clear the fault by the basic homeowner checks, if the switch or wiring needs replacing, or if any work requires opening the boiler casing, disturbing gas components, or carrying out electrical tests beyond simple visual checks. The engineer will have the correct spare parts, test equipment, and legal competence to work safely on gas appliances.

Important notes:

- Do not attempt to modify or bypass the flow switch or its wiring to force the boiler to run; this defeats safety controls and is dangerous.

- If the boiler is under warranty, contact your installer or the manufacturer-authorised service as inappropriate DIY work can void warranties. If you need heating or hot water urgently, arrange for a qualified call-out rather than continuing to attempt resets.