Ferroli A55 Fault Code: Causes, Fixes & Repair Costs
What does the Ferroli A55 fault code mean?
The A55 code is a hard lockout fault on Ferroli boilers pointing specifically to a problem with the AGC01 control board (PCB) — the main circuit board that manages all boiler operations. Because it begins with 'A', this is a manual-reset lockout: the boiler will not attempt to restart on its own and needs deliberate intervention before it fires again. Related codes in the same PCB fault family include A54 and A63, which also flag AGC01 control board issues, and F61, which is a blocking (auto-resetting) variant of a similar electrical fault. If your display shows any of these alongside A55, the diagnosis path is the same.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- Failed or damaged AGC01 PCB Common
The AGC01 control board itself has developed an internal fault — a failed component, a burnt track, or a short circuit on the board. This is the primary cause indicated by the A55 code. The board needs electrical testing with a multimeter by an engineer to confirm failure before replacement.
- Loose or damaged wiring to the PCB Sometimes
Vibration, heat cycling, or age can cause connector pins to work loose or wiring insulation to crack, breaking the circuit between the PCB and other components. An engineer will check every connector on the AGC01 board as this is sometimes the only fault and is far cheaper to fix than a full board replacement.
- Power supply or electrical surge issue Rare
A transient voltage spike — from a power cut, lightning nearby, or a faulty fused spur — can lock out the PCB without permanently damaging it. In these cases a single reset may clear the fault. If it returns, the board or wiring has sustained actual damage.
How to fix it
- Attempt a single manual reset DIY safe
Locate the reset button on your Ferroli's control panel — it is usually marked with an 'R' or a flame symbol with a line through it. Press and hold it for one to two seconds until the boiler attempts to restart. If the fault clears and the boiler runs normally, monitor it over the next hour or two.
- Do not reset more than two or three times DIY safe
If the A55 code returns within the same session, stop resetting. Repeatedly forcing the boiler to attempt ignition when there is a genuine PCB fault can cause secondary damage to components such as the fan or heat exchanger, turning a single repair into a much costlier job.
- Check your mains electrical supply DIY safe
Confirm the fused spur feeding the boiler is switched on and the fuse has not blown. Check your consumer unit to ensure no circuit breakers have tripped. A loss of clean mains power can cause a one-off PCB lockout that a reset will clear permanently.
- Call a Gas Safe registered engineer to test the PCB and wiring Gas Safe engineer
An engineer will use a multimeter to verify that mains voltage is reaching the AGC01 board correctly, then check every wiring loom connector for corrosion, looseness, or damage. If a loose connection is found it can often be repaired on the same visit. If the board itself has failed, it will need to be replaced — a job requiring safe isolation of both gas and electrics.
- PCB replacement if testing confirms board failure Gas Safe engineer
If wiring is intact but the AGC01 board has failed, the engineer will source a compatible replacement PCB, fit it, re-commission the boiler, and check combustion and gas pressure are within specification before leaving. This is the most common outcome when A55 keeps returning after a reset.
Parts you may need
- Ferroli AGC01 PCB (control board) · from £320
- Wiring loom / connector set · from £45
- Fused spur (external electrical) · from £15
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £150–£500, depending on the underlying cause.
Frequently asked questions
Can I fix a Ferroli A55 fault myself?
The only safe DIY action is a single manual reset using the button on the boiler's control panel. Everything beyond that — opening the casing, testing the PCB, replacing wiring, or fitting a new board — requires a Gas Safe registered engineer. Working on boiler electrics without the correct registration is illegal in the UK and potentially dangerous.
How much does it cost to fix a Ferroli A55 fault?
If the fault is just a loose wiring connector, you might pay £100–£180 covering the engineer's call-out and a short repair. If the AGC01 PCB needs replacing, parts typically cost around £300–£350 and labour adds £100–£180, putting the total in the region of £400–£500. These are the most likely repair scenarios for A55.
My Ferroli boiler is over 10 years old — is a PCB replacement worth it?
It depends on the boiler's overall condition and repair history. As a rough guide, if the repair quote exceeds 30–40% of what a new A-rated boiler would cost installed, replacement often makes better long-term financial sense. Ask your engineer for an honest assessment of the boiler's condition at the same time as the diagnosis visit.
What is the difference between Ferroli A54, A55, and A63 fault codes?
All three codes flag a fault related to the AGC01 control board and result in the same hard lockout condition. The specific sub-number reflects slightly different detection triggers within the board's self-diagnostic routine, but from a repair perspective the investigation and fix are identical: an engineer tests the PCB and wiring, then repairs or replaces whichever component has failed. If you see any of these three codes, follow the same steps described on this page.