Potterton E164 Fault Code: Causes, Fixes & Repair Costs
What does the Potterton E164 fault code mean?
The E164 code appears on Potterton boilers when the control board detects a problem with the domestic hot water (DHW) NTC (negative temperature coefficient) thermistor — the sensor responsible for measuring the temperature of your hot water. The fault can arise from either a short circuit or an open circuit within the sensor itself, meaning the boiler's electronics are either reading an impossibly low resistance (short) or getting no signal at all (open). In some cases the code can also point to an issue with the heating flow sensor or its associated wiring. Either way, the boiler cannot reliably monitor hot water temperature and will restrict or halt operation until the fault is resolved.
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 degraded DHW NTC thermistor Common
The DHW NTC sensor itself has broken down — either through age, heat cycling, or water ingress — and is producing a resistance reading outside the acceptable range for the boiler's PCB. This is the most common root cause of E164 and almost always requires the sensor to be replaced.
- Short circuit or open circuit in the sensor circuit Common
A short circuit causes the PCB to see near-zero resistance on the sensor line, while an open circuit means no signal reaches the board at all. Both conditions trigger E164. The fault may lie within the sensor body itself, or at any point along the wiring loom between the sensor and the PCB.
- Damaged, loose, or corroded wiring connections Sometimes
Vibration, moisture, or simply age can cause the wiring connectors at the sensor end or the PCB end to work loose or corrode. A poor connection can intermittently mimic a sensor failure even when the sensor itself is functioning correctly. Engineers will check the loom and connectors before condemning the sensor.
- Heating flow sensor fault Sometimes
In some Potterton models the E164 code can also reflect a fault with the heating flow sensor or its associated switch rather than the DHW sensor specifically. The diagnostic approach is the same — the engineer will test both sensors to identify which component is at fault.
- PCB fault misreading sensor data Rare
If the sensor and all wiring test correctly, the printed circuit board itself may have developed a fault on the input channel used to read the DHW sensor signal. This is an uncommon cause but should be considered when all other components check out.
How to fix it
- Reset the boiler DIY safe
Locate the reset button on your Potterton boiler's control panel — it is usually marked with a flame or reset symbol. Press and hold it for approximately 3–5 seconds until the boiler attempts to restart. Alternatively, switch the boiler off at the programmer or thermostat, wait 30 seconds, and switch it back on. If the E164 code clears and the boiler runs normally, monitor it over the next day or two. Do not reset more than two or three times in quick succession, as repeated resets without a fix can mask a developing problem.
- Check your gas supply is on DIY safe
Make sure your gas supply has not been interrupted. Check that other gas appliances in your home (hob, gas fire) are working normally. If there is no gas supply to the property, contact your gas supplier rather than attempting any boiler work.
- Inspect the boiler for obvious wiring issues — visually only Gas Safe engineer
A Gas Safe engineer will remove the boiler casing and visually inspect the wiring loom running to the DHW NTC sensor and any associated connectors. They will look for signs of chafing, heat damage, corrosion, or connectors that have worked loose. Do not remove the boiler casing yourself — this must be done by a registered engineer.
- Test the DHW NTC sensor resistance Gas Safe engineer
Using a multimeter, a Gas Safe engineer will measure the electrical resistance of the DHW NTC thermistor and compare the reading against the manufacturer's specification for the current water temperature. A reading that is out of range, or an open/short circuit reading, confirms sensor failure. This is technical work requiring access to the boiler internals and must not be attempted by a homeowner.
- Replace the faulty DHW NTC sensor (or heating flow sensor) Gas Safe engineer
If the sensor is confirmed faulty, the engineer will source and fit a compatible replacement NTC thermistor for your specific Potterton model. They will also check the heating flow sensor if the initial sensor test was inconclusive. After fitting, the boiler is tested to confirm the fault code has cleared and temperatures are being read correctly.
- Inspect and test the PCB if sensor replacement does not resolve the fault Gas Safe engineer
Should the fault code persist after a new sensor has been fitted and all wiring verified, the Gas Safe engineer will assess whether the PCB input circuit has failed. PCB replacement is a more significant repair and will be quoted separately. This step is only reached when all sensor and wiring checks have been exhausted.
- Call a Gas Safe registered engineer Gas Safe engineer
If a simple reset does not clear the E164 code, contact a Gas Safe registered engineer to diagnose and repair the fault. You can verify an engineer's credentials at www.gassaferegister.co.uk. Attempting to repair or replace internal boiler components yourself is unsafe and will invalidate your boiler warranty.
Parts you may need
- DHW NTC thermistor sensor (Potterton compatible) · from £25
- Heating flow NTC sensor · from £30
- Sensor wiring loom / harness · from £45
- Potterton PCB (if sensor checks pass) · from £180
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–£350, depending on the underlying cause.
Frequently asked questions
Can I fix the Potterton E164 fault myself?
The only safe DIY step is resetting the boiler once or twice via the reset button. All other work — removing the casing, testing the sensor, replacing wiring, or fitting a new component — must be carried out by a Gas Safe registered engineer. Working on boiler internals without registration is illegal in the UK and could void your home insurance.
How much does it typically cost to fix an E164 fault on a Potterton boiler?
For most homeowners the repair involves replacing the DHW NTC thermistor, and the total bill including parts and an engineer's labour usually falls between £150 and £350. The sensor itself is relatively inexpensive (typically £20–£50), so labour makes up the bulk of the cost. If the PCB turns out to be the root cause, costs can rise significantly — often £300–£600 or more — but this outcome is uncommon. Emergency or out-of-hours call-outs will also attract a premium on top of standard rates.
Will E164 stop my boiler from producing hot water or heating?
Yes, in most cases. Because the boiler cannot safely regulate DHW temperature without a working sensor signal, it will typically lock out or restrict operation to protect the system from overheating. You may lose hot water, central heating, or both until the fault is resolved.
Could the E164 fault come back after the sensor has been replaced?
It is uncommon for a new sensor to fail quickly. However, if an underlying wiring issue or a PCB fault was not identified at the time of repair, the code could reappear. An annual boiler service (typically £80–£120) helps catch early signs of sensor degradation, corrosion, or wiring wear before they cause a full breakdown.