Error E36

Safety precautions:

1) If you are not competent with gas appliances or mains electricity, stop and call a Gas Safe registered engineer. Working inside a boiler can be dangerous.

2) Before any physical checks isolate the electrical supply at the fused spur (switch off and, if possible, isolate the RCD). Do not work on the boiler with mains power applied.

3) Do not operate the boiler with the case removed after you have opened it; fully reassemble before restoring power and gas.

4) If you smell gas or suspect a gas leak, turn off the gas at the meter/isolating valve, ventilate the area, do not switch electrical items on or off, leave the property and call the gas emergency number immediately.

Initial homeowner checks (safe, quick checks you can do first):

1) Note the error code and try a single reset using the boiler reset button or switch. If it clears and stays cleared, monitor for recurrence. Repeated resets are not a fix.

2) Check the boiler display/LEDs and the system pressure gauge—if pressure is very low the boiler may behave unpredictably (E36 is a sensor fault, not a pressure fault, but it’s good to rule out obvious system issues).

3) Turn the boiler off and visually inspect the exterior for signs of water leaks around the boiler, staining or corrosion—water ingress can damage sensors and wiring.

4) If comfortable, remove any small access cover to visually check the external wiring to the boiler (mains fused spur is ON/OFF) but do not open the main boiler case unless you are competent. Look for loose, corroded or disconnected external connections.

If you are competent with basic electrical measurement and decide to progress (professional recommended):

1) Isolate and lock off the electrical supply to the boiler at the fused spur. Also shut off the gas supply if you will remove covers or work on internal components.

2) Remove the outer case/front panel following the manufacturer guidance. Keep screws and note orientation.

3) Locate the flow thermistor (usually clipped to the flow pipe or heat exchanger and connected to the PCB by a 2-pin push-on connector). Take photos before removing connectors so you can reconnect correctly.

4) Inspect the sensor and wiring for visible damage, corrosion, or water ingress. Inspect the connector: push-on terminals can be loose, pushed back or corroded. Tighten or re-seat if necessary.

5) With the electrical supply still isolated, remove the push-on connector and check continuity/resistance of the thermistor with a multimeter. Many thermistors are NTC devices — you should measure a finite resistance that changes with temperature (not infinite/open). The exact resistance specification is manufacturer-specific; if you read infinite (open circuit) the thermistor has failed. If you have the boiler manual or part spec, compare the measured resistance to the expected value at ambient temperature.

6) If the wiring to the PCB shows continuity but the sensor is open, replace the thermistor. Replacing typically involves unclipping the thermistor from the pipe, removing the push-on wires and fitting the new sensor in reverse order. Use a correct OEM or recommended replacement part.

7) If the thermistor measures OK but the boiler still reports E36, check the wiring continuity from the thermistor connector back to the control PCB and inspect the PCB connector for corrosion/damaged pins. An open at the connector, broken wire, or PCB fault could be the cause.

8) After replacing or reseating the sensor and wiring, re-fit the cover, restore electrical supply, and test the boiler. Clear the fault by reset and observe operation.

When to call a professional:

1) If the fault persists after you have reseated connectors or if you are unsure about any step, call a Gas Safe registered engineer. Replacing sensors and any work inside the boiler casing involves gas and mains electricity and should be done by a qualified engineer.

2) Call a professional if you find water ingress, a leaking heat exchanger, damaged wiring or a suspected PCB fault—these require specialist diagnosis and safe repair.

3) If the boiler is under warranty contact the manufacturer or the installer before doing internal repairs so you do not invalidate warranty terms.

Final notes:

- Do not repeatedly reset the boiler as a long-term solution.

- Document what you checked and take photos; this helps the engineer diagnose faster.

- The most common and likely fix is a failed thermistor or a loose/ corroded connector; however, wiring or PCB faults do occur and need professional attention.