Potterton BoilerFault Codes Guide
E119 · E133 · E160 · E125 · E168 · E128 · E130 · E153 — Wokingham expert repair guide
Your Potterton boiler is showing a fault code. Some you can fix yourself — others need a Gas Safe engineer. This guide tells you exactly which is which, written by Stuart Mundy, Gas Safe 599015, who has been repairing Potterton boilers across Wokingham and RG40 for over 20 years.
Potterton boiler fault codes — full guide
Potterton boilers — including the Promax, Performa, Gold and Suprima series — display alphanumeric fault codes when something goes wrong. Use this guide to understand what yours means, what you can safely try yourself, and when you need a Gas Safe engineer.
What it means
System water pressure has dropped below the safe minimum — typically below 1.0 bar. The boiler shuts down to protect itself from running dry.
Likely causes
- Radiators recently bled
- Minor leak in pipework or radiator valve
- Failing expansion vessel
- Pressure relief valve discharged
How to fix
- Locate the filling loop (silver braided hose under the boiler)
- Open both valves slowly until pressure reads ~1.5 bar
- Close both valves firmly
- Press the reset button
What it means
The boiler failed to ignite or the flame was lost during operation. A safety lockout has been triggered.
Likely causes
- Gas supply interrupted or meter off
- Frozen condensate pipe (common in Wokingham winters)
- Faulty ignition electrode or lead
- Gas valve fault
- Blocked or restricted flue
What to try
- Check other gas appliances are working
- In cold weather, check the condensate pipe (plastic pipe exiting outside) — defrost with warm water if frozen
- Press and hold reset for 3 seconds
What it means
The boiler's fan is not running at the correct speed or has stopped. The fan is a safety-critical component — it vents combustion gases outside. The boiler will not fire without it.
Likely causes
- Fan motor failure
- Loose or damaged wiring to the fan
- PCB not sending correct signal
- Blockage in the flue restricting airflow
What will happen
Stuart will test fan speed, wiring continuity and PCB outputs to pinpoint whether it’s the fan itself, the wiring harness or a PCB fault. Fan replacement is straightforward if wiring and PCB are healthy.
What it means
The boiler cannot detect sufficient water movement through the heating system. It shuts down to prevent overheating.
Likely causes
- Seized or failing circulating pump
- Airlock in pipework or radiators
- Heavy sludge/magnetite blockage
- Closed isolation valves
- Faulty flow sensor
What to try
- Check all radiator valves are fully open
- Bleed all radiators to release airlocks
- Reset the boiler and check if it fires
What it means
The gas valve is not opening or closing correctly. This is a critical safety component — the boiler will lock out and refuse to fire.
Likely causes
- Gas valve solenoid failure
- Wiring fault to the valve
- PCB not sending correct signal
- Gas valve seized (often age-related)
What will happen
Gas valve replacement is a common repair on older Potterton Promax and Performa models. Stuart carries common valves on the van. The PCB will also be tested to confirm it’s sending the correct voltage to the valve.
What it means
The boiler’s printed circuit board (PCB) has detected an internal electrical fault. The PCB is the control centre of the boiler — managing all components and safety systems.
Likely causes
- PCB component failure
- Moisture ingress
- Power surge damage
- Age-related failure (common on Promax models over 10 years)
What will happen
Stuart will test individual PCB outputs before condemning the board — sometimes it’s a wiring fault rather than the PCB itself. PCB replacement on Potterton Promax and Performa is a well-known repair with good parts availability.
What it means
The boiler has detected an overheat condition, or the NTC thermistor (temperature sensor) is faulty and sending incorrect readings to the PCB.
Likely causes
- Faulty NTC thermistor
- Blocked heat exchanger causing hot spots
- Poor circulation leading to overheating
- Scale build-up on heat exchanger (very common in Wokingham)
What will happen
NTC sensor replacement is a quick repair if the sensor is the fault. However if scale build-up on the heat exchanger is causing genuine overheating, a powerflush and inhibitor treatment will be recommended alongside the repair.
What it means
The flue overheat thermostat or a secondary safety thermostat has tripped. This indicates the flue gases are running too hot — a safety-critical condition.
Likely causes
- Blocked or restricted flue
- Incorrect flue installation
- Safety thermostat failure
- Combustion issue causing excess heat
What will happen
Stuart will inspect the full flue run for blockages or damage, test combustion quality with a flue gas analyser, and test the safety thermostat. Flue issues must be resolved before the boiler is returned to service.
Potterton models we service and repair in Wokingham
Frequently asked questions
What does E119 mean on a Potterton boiler?
What does E133 mean on a Potterton boiler?
Is my Potterton boiler too old to repair in Wokingham?
Does hard water in Wokingham affect Potterton boilers?
How much does a Potterton boiler repair cost in Wokingham?
Can you repair my Potterton boiler under warranty?
Potterton boiler showing a fault?
Fixed today, first time
Fixed price from £96 · Exact arrival time · 90% first-time fix · Parts on the van · Gas Safe 599015
Common Potterton Boiler Fault Codes
Potterton boilers (like the Promax, Performa, and Gold series) use alphanumeric fault codes to indicate specific issues. Here are the most common ones we encounter in Wokingham homes:
E119 – Low Water Pressure
What it means: The boiler’s water pressure is below the safe minimum level (typically under 1.0 bar).
Likely causes:
Bleeding radiators recently
Minor leak in pipework
Loss of pressure over time
Quick fix:
Locate the filling loop (silver braided hose)
Open the valves slowly to increase pressure to ~1.5 bar
Close both valves and reset the boiler
If pressure keeps dropping, it may indicate a hidden leak or expansion vessel fault.
E133 – Ignition Failure / Gas Supply Issue
What it means: The boiler is failing to ignite or the flame has been lost.
Possible causes:
Gas meter off
Frozen condensate pipe
Faulty ignition lead or gas valve
Blocked flue
What to try:
Check your gas supply (other gas appliances working?)
Defrost the condensate pipe if it’s cold outside
Press and hold the reset button
If the fault recurs, you’ll likely need an engineer to investigate ignition components or valve function.
E160 – Fan Fault
What it means: The fan isn’t running or is malfunctioning — a safety issue since the fan expels flue gases.
You’ll need a heating engineer to:
Test fan wiring and PCB
Replace the fan if needed
Check for blockages in the flue
E125 – Circulation Fault
What it means: The boiler detects a lack of water movement through the system.
Common causes:
Airlock in pipework
Failed pump
Dirty system water/sludge
Fix:
Try bleeding radiators. If that doesn’t help, call a professional — pump replacement or a power flush may be needed.
When to Call us your Local Gas Safe Engineer in Wokingham
If you're seeing recurring fault codes, unusual noises, smells, or a total system shutdown, it's time to call a qualified heating engineer.
At Thermo-Tec Plumbing & Heating, we’re Gas Safe registered and experienced with Ideal fault codes. We cover Wokingham, Lower Earley, Woosehill, and surrounding villages.
Need a Potterton Boiler Repair in Wokingham?
If your Baxi boiler is showing a fault code or refusing to fire up, we’re here to help.
Call Thermo-Tec today on 07850116944 for Potterton boiler repairs in Wokingham and surrounding areas.
FAQs – Potterton Faults
Q: What should I do if my Potterton boiler shows E119?
A: Top up the pressure via the filling loop. If it drops again, get a leak inspection.
Q: Can I fix E133 myself?
A: Check for frozen pipes or gas issues, then reset. Persistent faults need an engineer.
Q: Is my Potterton boiler too old to fix?
A: We can repair many models, but if your unit is over 15 years old, a replacement may be more cost-effective.