Biasi E07 Fault Code: Causes, Fixes & Repair Costs
What does the Biasi E07 fault code mean?
The E07 (also displayed as ER07 on some Biasi models) fault code indicates that the boiler's PCB has detected a problem with the domestic hot water (DHW) NTC temperature sensor — sometimes referred to as the hot water probe. This sensor continuously feeds temperature readings back to the PCB so the boiler can regulate hot water output safely. When those readings fall outside acceptable limits, or stop arriving altogether, the PCB assumes something is wrong and shuts the boiler down into lockout to prevent potential damage. In practical terms: your boiler will stop working and the E07 or ER07 code will sit on the display until the underlying fault is identified and fixed. On some newer Biasi models this fault may appear as E164 or A07, which carries the same meaning — a DHW temperature sensor fault or excessive hot water temperature.
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
- Faulty or failed DHW NTC temperature probe Common
The DHW NTC probe is the single most common cause of this fault. Over time the probe can degrade, develop an internal break, or simply fail, causing it to send wildly incorrect readings or no signal at all to the PCB. The boiler responds by locking out. The probe will need to be tested with a multimeter and, if confirmed faulty, replaced.
- Loose, corroded, or damaged wiring connections Common
Even if the probe itself is in good condition, a loose connector, corroded terminal, or damaged wire between the probe and the PCB can mimic a sensor failure entirely. Vibration over time and general wear can cause connections to work loose. A Gas Safe engineer can test the full circuit with a multimeter and resecure or replace any suspect wiring.
- Faulty PCB Sometimes
If the probe and its wiring both test correctly, attention turns to the PCB. A PCB that has developed a fault on the input channel monitoring the DHW sensor may misread a perfectly good signal and trigger E07 incorrectly. PCB faults are less common than sensor or wiring issues but must be considered once the sensor circuit has been ruled out.
- Limescale build-up on the secondary heat exchanger (hard-water areas) Sometimes
In areas with hard water, limescale can accumulate inside the secondary heat exchanger, causing localised overheating near the DHW probe. This can produce erratic temperature readings that trigger E07. A powerflush or descale of the secondary heat exchanger may resolve the fault if this is the root cause.
How to fix it
- Attempt a single boiler reset DIY safe
Locate the reset button on the Biasi boiler's front panel — it is usually marked with a flame or reset symbol. Press and hold it for around 5–10 seconds until the display changes and the boiler attempts to restart. Allow up to 10 minutes for the boiler to complete its start-up sequence. If the E07 code returns immediately or within a short time, do not keep resetting repeatedly — a reset clears the lockout but does not fix the underlying fault. Move on to the next step.
- Check that your gas supply is working DIY safe
Verify that other gas appliances in your home (such as a gas hob) are working normally. If there is no gas supply to the property, contact your gas supplier rather than an engineer. If other appliances work fine, the gas supply is not the issue here.
- Do not attempt to open the boiler casing Gas Safe engineer
Accessing the DHW NTC probe, wiring, or PCB requires removing the boiler casing. Working inside a gas appliance without Gas Safe registration is illegal in the UK and potentially dangerous. Do not attempt this yourself.
- Call a Gas Safe registered engineer to diagnose the fault Gas Safe engineer
A qualified engineer will use a multimeter to measure the resistance of the DHW NTC probe across its expected temperature range and to test continuity and integrity of the wiring loom. This tells them definitively whether the probe, its wiring, or the PCB is responsible for the E07 code.
- Engineer replaces the faulty component Gas Safe engineer
If the probe is confirmed faulty, it will be replaced with the correct Biasi-compatible NTC sensor. If wiring is the issue, connectors will be resecured or the harness repaired. If limescale is suspected, a descale or powerflush of the secondary heat exchanger may be recommended. In the less common scenario where the PCB is at fault, the engineer will advise on replacement costs versus the age of the boiler.
Parts you may need
- Biasi DHW NTC temperature probe/sensor · from £35
- Wiring harness / connector repair kit · from £20
- Secondary heat exchanger (combi) · from £120
- Replacement PCB · from £220
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 £140–£320, depending on the underlying cause.
Frequently asked questions
Can I fix the Biasi E07 fault myself?
Unfortunately not. Diagnosing and replacing the DHW NTC probe or any associated wiring requires opening the boiler casing, which legally constitutes work on a gas appliance in the UK. Only a Gas Safe registered engineer is permitted to do this. The one thing you can safely try yourself is a single reset — but if the code comes straight back, stop resetting and call an engineer.
How much does it cost to repair a Biasi E07 fault?
For the most common repair — replacing the DHW NTC temperature sensor and any associated wiring work — most UK homeowners pay somewhere between £140 and £320 including parts and labour. If the fault turns out to be a failed PCB, costs are higher, typically £350–£550 or more depending on the model. On older Biasi boilers, if a PCB quote is approaching £500, it is worth getting a new boiler quote at the same time, as replacement can make more financial sense in the long run.
My boiler shows ER07 rather than E07 — is it the same fault?
Yes, ER07 and E07 refer to the same underlying fault on Biasi boilers. The ER prefix is simply how certain Biasi display panels render the error — the meaning (DHW NTC probe failure) and the fix are identical. Some newer Biasi models may show this fault as E164 or A07, which also indicates a DHW temperature sensor issue.
Will the E07 fault affect my central heating as well as hot water?
Because E07 is specifically linked to the domestic hot water temperature sensor, it primarily affects the hot water circuit. However, because the boiler enters full lockout when E07 triggers, both your hot water and central heating will be unavailable until the fault is cleared. Once the sensor or wiring issue is repaired and the boiler is reset by the engineer, both functions should return to normal.