Error E34

Safety precautions:

1. If you suspect an electrical fault, switch the boiler off at its external isolator and the consumer unit. Do not open the boiler cover or attempt internal repairs. Only a qualified Gas Safe engineer and a competent electrician should remove the casing or work on gas/electrical internals.

2. If you see signs of severe electrical problems (sparks, burning smell, tripping RCDs/MCBs, persistent power loss), isolate the mains and contact a qualified electrician and your electricity supplier immediately.

Initial checks a homeowner can do:

1. Check whether other electrical appliances or lights in the house are dimming, flickering or behaving oddly. If so, this indicates a wider low-voltage or supply problem rather than the boiler alone.

2. Check your household consumer unit (fuse box) for tripped breakers or RCD trips. Reset any tripped breakers and test whether that clears the boiler fault (do not keep resetting a breaker that trips repeatedly).

3. Check the boiler’s external isolator/fused spur is switched on and the fuse is intact. Replace a blown spur fuse with the correct rating only if you are confident and the isolator is de-energised.

4. Try a simple reset of the boiler using the manufacturer’s reset procedure (single reset only). If the fault is caused by a transient voltage dip, a single reset might clear it. Do not attempt multiple rapid resets; too many resets in a short time can cause further lockouts.

Specific diagnostic steps (do not open the boiler; only open the fused spur or consumer unit if competent):

1. Observe and record: note the time(s) the E34 code appears and any concurrent symptoms (lights dimming, heavy appliance use like washing machine, weather/ storms). This information is useful for your electrician or network operator.

2. Check other circuits/sockets: plug a lamp or a mains tester into several sockets. If lights are dim across the house or multiple sockets show issues, the problem is likely supply-side.

3. If you are electrically competent and have a properly rated digital multimeter, measure the voltage at a nearby socket or at the boiler fused spur with the boiler powered on. Measure L-N (line to neutral) and L-E (line to earth). Normal UK supply should be around 230 V (±10%); anything consistently below 180 V confirms a real low-voltage condition. Only perform measurements if you are trained and comfortable with mains voltage testing.

4. If voltage is low at the fused spur or sockets: contact your electricity distribution network operator (DNO) or supplier to report low-voltage or supply dips. They can check the external supply and the service head.

5. If voltage is normal at the fused spur but the boiler still shows E34: do not open the boiler. This may indicate an internal wiring/connection fault at the appliance isolator or internal electronics reporting incorrectly. Contact a qualified electrician to check the isolation switch wiring, and a Gas Safe engineer to inspect the boiler’s control box and mains connections.

Potential remedial actions by professionals (you should arrange these, do not attempt yourself):

1. Electrician will inspect and tighten incoming supply connections at the consumer unit and the boiler fused spur, test for voltage drops under load, and identify any shared neutral or wiring issues. If required, they will isolate and repair defective wiring.

2. If the problem is supply-side (DNO issue), the network operator will repair the external fault or replace/adjust equipment to restore correct voltage.

3. Once mains voltage is restored and stable, a Gas Safe engineer should inspect the boiler for any damage to the control PCB or other components and clear the fault code. They will run full safety and combustion checks before returning the boiler to service.

Important notes and when to call a professional:

1. Do not open the boiler casing or attempt internal electrical or gas repairs. That work must be carried out by accredited professionals (a qualified electrician for mains wiring, and a Gas Safe registered engineer for boiler internals).

2. If you confirm or strongly suspect sustained mains voltage under 180 V, contact your electricity supplier/DNO and an electrician. If the E34 code remains after the supply has been corrected, arrange for a Gas Safe engineer to inspect and repair the boiler.

3. Keep a written record of times, voltage readings (if taken), and any communications with your supplier or engineers – this helps with diagnosis and any follow-up claims.

If you want, provide the following to the electrician/Gas Safe engineer: the boiler model (Keston C36 Combi), the E34 code, the times it appeared, whether other appliances were affected, and any voltage readings you recorded.