Error E385

Safety precautions:

1. Turn the boiler off at the boiler on/off switch and at the fused isolator before touching anything. If you are unsure where the isolator is, switch the boiler off at the consumer unit (trip the relevant MCB) and switch off the appropriate RCD if necessary.

2. Do not remove the boiler cover or work on internal wiring unless you are a qualified engineer. Working on gas or mains electricity is dangerous and should be left to Gas Safe and qualified electricians.

3. If you smell gas or suspect a gas leak, leave the property immediately and call the gas emergency number and a Gas Safe engineer. Do not use electrical switches or phones near the leak.

Initial homeowner checks you can do safely:

1. Note the exact error code, when it started, and any symptoms (intermittent hot water, pressure drops, lights dimming when heating runs). This information is useful for an engineer.

2. Reset the boiler once: switch off at the boiler, wait 30 seconds, then switch back on and attempt a reset using the boiler reset button as per the manual. If the fault returns immediately or repeatedly, do not keep resetting.

3. Check the house consumer unit for tripped MCBs or RCDs and reset if safe to do so. If the breaker trips again, don’t repeatedly reset it.

4. Check the boiler fused isolator (fused spur) and any accessible inline fuse to see if a fuse has blown. Replace only if you are competent and you use the correct rating fuse and the isolator was off while changing it.

5. See if other high-power appliances in the house (cookers, showers, ovens) cause lights to dim or the problem to occur — this can indicate a general supply voltage or load issue.

6. Check if the issue follows a mains power cut or local electrical works; if so it may be a temporary supply problem from the utility provider.

Specific diagnostic steps and fixes (homeowner-friendly and engineer steps):

Homeowner-level actions (limited):

1. After the basic checks above, if resetting and checking fuses/circuits didn’t help, switch the boiler off and contact a qualified engineer. Do not open the boiler enclosure or touch internal connectors.

2. If you have a reliable portable appliance or lamp, check several sockets in the home to see if the mains voltage seems low (lights dim, appliances run slower). This is not a substitute for a voltage reading but can indicate a general supply problem.

Recommended engineer diagnostics and actions (to be carried out by a qualified heating engineer and/or electrician):

1. Measure incoming mains voltage at the boiler fused spur and at the consumer unit under load and no-load conditions using a calibrated meter. Confirm voltage and frequency (should be ~230V nominal, >195V when under load for this boiler, and ~50Hz).

2. Inspect the incoming supply cable, consumer unit connections and the fused isolator for loose connections, signs of overheating, corrosion or poor terminations. Tighten and correct any poor connections.

3. Check neutral and earth continuity and ensure there are no shared neutrals or overloaded circuits causing voltage drop.

4. Verify the boiler’s internal PSU/transformer and PCB voltages once safe to do so. Check for bulging capacitors, burn marks or component failure on the PCB that could cause incorrect voltage sensing. Replace PCB or PSU only if confirmed faulty by the engineer.

5. Test the boiler under load (call for heat/hot water) and monitor mains voltage to see if voltage drops when the boiler attempts to fire — this helps identify whether the problem is external supply or an internal heavy load/short.

6. Inspect associated components that might draw excessive current (pump seized, fan fault, shorted gas valve) which could cause a heavy transient current draw and apparent undervoltage. Repair or replace faulty components.

7. If the incoming supply from the utility is low, the homeowner should contact their electricity supplier and/or an electrician to address the low supply or supply-side faults.

When to call a professional:

1. If the error persists after a basic reset and checking fuses/breakers, call a Gas Safe registered heating engineer and, if electrical supply is suspected, a qualified electrician. Anything involving internal boiler wiring, gas valves, PCB replacement or measuring mains at the boiler must be done by professionals.

2. If the engineer suspects damage to the PCB, transformer or other control electronics, these parts should be replaced by a qualified engineer and tested thoroughly.

Final notes:

1. Do not keep resetting the boiler repeatedly; persistent undervoltage can damage electronics and create unsafe conditions.

2. Record the error code, date/time and any preceding events (power cuts, storms, electrical work) to give to the engineer. This speeds diagnosis.

3. Priority is safety: if you are in any doubt about working with mains electricity or gas, isolate the boiler and contact the appropriate qualified professionals (Gas Safe engineer and an electrician).