Boiler
E7
The E7 error code on a Glow-worm boiler indicates a fault with the fan or air pressure circuit — it’s a moderately serious fault that will lock out your boiler and cut off heating and hot water until resolved.
What does this error mean?
The E7 code tells you that your boiler’s control board has detected a problem with the fan or the air pressure sensing system (via the pressure switch/air pressure switch). The boiler expects the fan to reach a certain speed and create negative pressure before ignition — if this isn’t confirmed, it shuts down as a safety measure. In plain terms: your boiler thinks air isn’t flowing correctly through the flue system, so it refuses to fire up.
Est. repair cost
£80–£350 for professional repair depending on faulty component (pressure switch vs fan replacement)
🔍 Likely causes
🛠️ Step-by-step fix
Step 1 — Reset the boiler: Press and hold the reset button (usually marked with a flame or ‘R’) for 3–5 seconds. If the boiler fires up and runs normally, monitor it closely for recurrence. A one-off lockout can happen; a repeated E7 fault means there’s an underlying issue.
Step 2 — Check your flue terminal outside: Safely look at the external flue outlet (typically on a wall or roof). Remove any visible blockage such as leaves, debris, or a bird nest. Do not attempt to access the flue pipe internally — this is Gas Safe engineer territory.
Step 3 — Check for a frozen condensate pipe (winter only): If temperatures have been below freezing, your external condensate pipe may be frozen solid. Thaw it carefully by pouring warm (not boiling) water over the external section of pipe. Once clear, reset the boiler.
Step 4 — Do not attempt internal repairs: If the above steps don’t resolve the E7 fault, do not open the boiler casing. The fan, pressure switch, tubing, and PCB all sit inside the boiler and must only be inspected and replaced by a Gas Safe registered engineer.
Step 5 — Call a Gas Safe engineer: Book a qualified engineer and quote the E7 fault code. This gives them a head start — they’ll likely arrive with a replacement fan or pressure switch, the two most common fixes.
📞 When to call a professional
If a reset and a quick external flue check don’t clear the fault, stop and call a Gas Safe registered engineer — do not attempt to open the boiler casing or interfere with the fan or gas components. Tell the engineer you have a Glow-worm boiler showing an E7 fault code, and let them know how often it has locked out. Working on gas appliances without Gas Safe registration is illegal under UK law and extremely dangerous.
⚖️ Repair or replace?
A fan replacement on a Glow-worm boiler typically costs £150–£350 including labour; a pressure switch repair is cheaper at £80–£200. If your boiler is under 10 years old and otherwise reliable, repair is almost always the right call. If it’s over 12–15 years old and this isn’t the first fault, replacement with a modern A-rated condensing boiler (typically £1,800–£3,500 installed) is worth serious consideration — you’ll likely save on energy bills and avoid escalating repair bills.