If your Biasi boiler is displaying an error code on its screen, don’t panic – understanding Biasi boiler error codes is the first step to getting your central heating system or hot water back up and running quickly.
These fault codes are designed by the manufacturer to pinpoint specific issues in popular models like the Biasi Riva Compact, Advance Plus, ActivA, Garda HE, and Inovia.
In this guide, I’ll explain the most common Biasi boiler fault codes, along with their causes and practical fixes.
Many issues can be resolved with simple troubleshooting, while others require a Gas Safe registered engineer for safety reasons.
What Should You Do When a Biasi Boiler Fault Code Appears?
When a Biasi boiler fault code appears, the boiler often enters lockout mode for safety. Start by noting the exact code (e.g., ER 01, ER 03 + flashing light). Try a simple reset by pressing and holding the reset button for 3-5 seconds (check your model manual).
If the code persists, avoid repeated resets – this could indicate a deeper issue. Always prioritise safety: if you smell gas, turn off the supply and call the National Gas Emergency Service on 0800 111 999.
How Do You Reset a Biasi Boiler Safely?
To reset a Biasi boiler safely, locate the reset button on the front panel, press and hold it for 5–10 seconds until the display changes or the boiler restarts. Wait up to 10 minutes for the ignition sequence. Never keep resetting more than twice in a row – repeated failed ignitions can flood the combustion chamber with gas.
What Does the E133 Error Code (or ER01 with No Flame) Mean on a Biasi Boiler?
Error code E133 (or ER01 shown with a red lockout light) means the boiler has failed to detect a flame after several ignition attempts – essentially an ignition lockout.
Common Causes of E133 / ER01
- Frozen condensate pipe (very common in winter)
- No gas reaching the boiler (meter off, credit run out on prepayment meter, or frozen gas pipe)
- Faulty ignition electrode or spark generator
- Gas valve not opening correctly
How to Fix E133 – Frozen Condensate Pipe (DIY)
- Find the white plastic condensate pipe outside (usually 22mm or 32mm exiting the wall).
- Pour lukewarm water (never boiling) over the frozen section until it thaws.
- Reset the boiler once water flows freely.
- Wrap the pipe with lagging or heat tape to prevent it happening again.
How to Fix E133 – No Gas Supply (DIY)
- Check other gas appliances (hob or fire) – if they don’t work, top up prepayment meter or call your supplier.
- Look for a gas isolation valve under or beside the boiler – make sure it’s open (handle in line with pipe).
- If outside meter is frozen, gently warm with a hot water bottle or hairdryer.
How to Fix E133 – Electrode or Gas Valve Fault (Gas Safe Engineer Needed)
A qualified engineer will clean or replace the ignition electrode (£120–£220) or test/replace the gas valve (£250–£450).
What Does the A01Error Code Mean on a Biasi Boiler?
Error code A01 means ignition failure – identical in meaning to E133/ER01 on newer firmware models.
What Does the E110 or A02 Error Code Mean on a Biasi Boiler?
Error code E110 or A02 means the safety thermostat has tripped because the boiler has overheated.
Common Causes of E110 / A02
- Low system water pressure
- Seized or slow-running pump
- Blocked primary heat exchanger (sludge or limescale)
- Airlock in the system
How to Fix E110 – Low Water Pressure (DIY)
- Find the filling loop (flexible silver hose or built-in key under the boiler).
- Slowly open both valves until the pressure gauge reaches 1.2–1.5 bar.
- Close valves tightly and reset the boiler.
How to Fix E110 – Pump or Circulation Problem (Engineer)
An engineer may need to free the pump, fit a new one (£280–£420), or carry out a powerflush (£350–£600).
What Does the E118 or A03 Error Code Mean on a Biasi Boiler?
Error code E118 or A03 means low primary circuit water pressure (below 0.4–0.6 bar).
Common Causes of E118 / A03
- Leak on the heating system or pressure relief valve dripping outside
- Recently bled radiators without repressurising
- Faulty pressure sensor
How to Fix E118 – Top Up Pressure (DIY)
Follow the same repressurising steps as E110 above. Check outside for water dripping from the orange pressure relief pipe – this usually means a faulty expansion vessel or pressure relief valve.
What Does the A04 or E154 Error Code Mean on a Biasi Boiler?
Error code A04 or E154 means a problem with the fan or air pressure switch (APS) – the boiler cannot confirm correct ventilation.
Common Causes of A04 / E154
- Blocked or obstructed flue terminal (leaves, snow, wasp nest)
- Faulty fan motor
- Broken air pressure switch or blocked venturi
How to Fix A04 – Blocked Flue (DIY if safe)
Carefully clear any visible debris from the external flue terminal. Do not climb ladders if unsafe.
How to Fix A04 – Fan or APS Fault (Engineer)
Replacement fan costs £220–£380; air pressure switch £120–£200.
What Does the E164 or A07 Error Code Mean on a Biasi Boiler?
Error code E164 or A07 means a fault with the domestic hot water (DHW) temperature sensor or excessive hot water temperature.
Common Causes
- Failed hot water NTC sensor
- Heavy limescale in the plate heat exchanger (hard water areas)
Fix
Sensor replacement (£140–£250) or descaling/powerflush of secondary heat exchanger.
FAQs
Do Biasi boilers show different codes on older vs newer models?
Yes – older Biasi models (e.g. Riva Plus, Garda) use ER01, ER02 etc., while newer Inovia and Advance Plus models use E-codes (E133, E110, E118). The underlying problems are the same.
Will my Biasi boiler lose its warranty if I reset it myself?
No. Resetting and repressurising are considered normal user actions and do not affect the warranty. Only opening sealed components or gas-carrying parts would invalidate it.
Why does my Biasi boiler keep showing an error code after an engineer visit?
The most common reason is an intermittent fault (e.g. loose wiring or failing PCB) or a secondary issue that wasn’t spotted on the first visit. Ask for a follow-up under the original call-out warranty (most companies give 30 days).
Are Biasi parts easy to get in the UK in 2025?
Yes – Biasi spare parts are widely stocked by Parts Center, HRPC, and most local merchants. Popular items like pumps, PCBs, and sensors are usually next-day delivery.
Can smart thermostats cause error codes on Biasi boilers?
Very rarely, but incorrect wiring of controls such as Nest, Hive or Tado can cause communication errors or prevent the boiler firing. Always use a qualified installer for smart control upgrades.
The Boilers2Go Team
With years of experience in boilers and home improvements in general, Myles Robinson is a passionate advocate for making home heating simpler, safer, and more affordable for households across the UK. With years of experience in the heating industry, Myles combines hands-on knowledge with a focus on customer-first service, helping homeowners choose the right boiler, understand their systems, and keep their heating running efficiently all year round. His articles break down complex topics into clear, practical advice you can trust.