Error E385

Safety precautions:

1. If you smell gas, leave the building immediately and call your gas emergency number — do not operate electrical switches or the boiler. 2. Do not attempt mains electrical work or open live electrical terminals unless you are a qualified electrician. 3. Do not attempt to service or repair gas components, ignition, gas valve or PCB unless you are Gas Safe registered. 4. Isolate the boiler at its electrical switch before removing any panels for visual inspection; however, even with the isolator off, do not touch wiring unless qualified.

Initial homeowner checks you can safely do:

1. Note the full error code and any other codes displayed and the time it occurred. This information helps the engineer. 2. Check the boiler’s local isolator switch (usually a fused spur or switch near the boiler): ensure it is ON. 3. Check your house consumer unit (fuse box) for any tripped MCBs/RCDs and reset them if safe to do so. 4. Try a simple boiler reset using the manufacturer’s reset procedure (usually hold/reset button for 3–5 seconds) and wait for the boiler to attempt restart. 5. Observe whether other household appliances are showing strange behaviour (lights dimming, appliances restarting, loss of power) which suggests a wider electrical supply problem. 6. If you have a plug-in mains voltage monitor or a simple mains tester, you can use it to check for obvious mains problems at a socket; this is not a substitute for a proper measurement by a qualified electrician.

Specific diagnostic and practical steps (homeowner + guidance to professionals):

1. Simple reset sequence (homeowner): turn the boiler off at the isolator and at the room thermostat, wait 30–60 seconds, turn the isolator back on and then the boiler on; try a reset. If E385 clears and stays cleared, monitor operation for recurrence. If it returns, proceed to next steps. 2. Check for intermittent loads: switch off large appliances (electric showers, cookers, EV chargers, car chargers, immersion heaters) one at a time to see if a heavy load on the same electrical supply correlates with the boiler fault. If the fault occurs when a heavy load runs, this suggests local supply or circuit overload. 3. Visual inspection (homeowner): with the isolator off and only if competent, check the fused spur for obvious damage or a blown fuse. Replace only the correct fuse type and rating if blown. Do not open boiler wiring compartments.

4. Call a qualified electrician to measure incoming supply voltage and frequency correctly at the consumer unit and at the boiler terminals. The electrician should check: a) whether the mains voltage consistently falls below the manufacturer’s threshold (around 195 V) or shows large dips, b) the integrity of the neutral and earth connections, c) shared circuits or overloaded ring/mains supplying both the boiler and heavy appliances, d) the condition of the fused spur or dedicated circuit feeding the boiler. 5. If the electrician finds supply issues, they should resolve loose connections, supply-side faults, or advise contacting the distribution network operator (DNO) if the problem is outside your property (e.g. neighbourhood low voltage from the mains provider). 6. If the electrical supply checks as stable, call a Gas Safe registered heating engineer to inspect the boiler internals: they will check the boiler’s internal power supply components (transformer/regulator), PCB and connectors, gas valve operation, and any related sensors that may behave erratically under poor voltage. They can also test the boiler under load and replace faulty components if required.

When to call a professional urgently:

1. If the E385 fault persists after a basic reset and initial checks. 2. If other electrical issues are present in the property (lights dimming, other appliances failing, repeated tripping). 3. If you smell gas or detect burning smells, or if the boiler shows additional fault codes impacting ignition or gas supply. 4. If an electrician discovers unstable/low mains voltage or dangerous/loose wiring. 5. If the boiler repeatedly locks out or runs intermittently — stop using the boiler until inspected to avoid damage.

Important notes and record keeping:

1. Do not attempt internal electrical or gas repairs yourself. 2. Keep a clear record of the error code, any other codes, when it happened, and what electrical activity was happening in the house at the time — this helps the engineers diagnose intermittent supply issues. 3. Ask the attending electrician/engineer to test and confirm supply voltage at the boiler terminals and provide written findings. 4. If the issue is a supply-side problem (external), your DNO may need to be involved; if it’s internal, the electrician and Gas Safe engineer will coordinate repair or part replacement. 5. Repeated under-voltage events can damage the boiler PCB and other components, so persistent or recurring E385 should be treated as a priority for professional investigation.