Worcester Bosch 1065 Fault Code: Causes, Fixes & Repair Costs
What does the Worcester Bosch 1065 fault code mean?
Fault code 1065 on a Worcester Bosch boiler indicates that the boiler's control board cannot obtain a valid signal from the water pressure sensor. Either the sensor has lost its electrical connection — due to a loose or detached wiring plug — or the sensor itself has failed and is returning no reading or an erroneous one. Because the pressure sensor is responsible for confirming safe operating conditions in the primary circuit, the boiler blocks operation as a precaution until a reliable reading is restored. This is a blocking-type fault rather than a full lockout, but the effect is the same: the boiler will not fire until the issue is resolved.
General guidance only — not a substitute for professional advice. 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
- Loose or disconnected wiring connector Common
The most frequent cause. Vibration from normal boiler operation can gradually work a wiring plug loose from the pressure sensor terminal. The control board receives no signal and raises the fault. An engineer can often resolve this simply by reseating the connector firmly — no parts required.
- Failed pressure sensor Common
Over time, the sensor's internal components degrade. A failed sensor may output a flat zero, an out-of-range voltage, or an intermittent reading that the PCB rejects. The sensor will need to be replaced. This is more likely on boilers that are several years old or have seen heavy use.
- Damaged sensor wiring loom Sometimes
The cable running to the sensor can develop a short circuit, open circuit, or chafing damage — particularly if it passes near a hot component or has been pinched during a previous repair. The fault code behaves identically to a sensor failure, so an engineer will need to trace the wiring carefully.
- Incorrect sensor installation position Rare
If the boiler has been recently serviced or had internal work done, the sensor may have been refitted incorrectly or in the wrong port. This can cause it to read implausibly low or high pressure, prompting the block.
- PCB communication fault Rare
In rare cases the pressure sensor and its wiring are both intact, but the PCB input circuit that reads the sensor signal has failed. This is an uncommon cause but should be considered if replacing the sensor does not clear the fault.
How to fix it
- Check your gas supply and reset the boiler once DIY safe
Before assuming a component fault, confirm that your gas supply is on (check another gas appliance). Then press and hold the reset button on your boiler for the time specified in your user manual — typically around 3 seconds. Allow the boiler a minute to restart. If the fault clears and does not return within a short time, no further action may be needed. Do not reset more than two or three times; repeated resets without a fix can mask a deeper problem.
- Check the system pressure gauge DIY safe
Look at the pressure gauge on the front of your boiler. It should normally read between 1.0 and 1.5 bar when the system is cold. A reading that is very low (below 0.5 bar) or very high (above 2.5 bar) may be contributing to abnormal sensor readings. If pressure is low, you can top it up using the filling loop — consult your boiler's user guide for the correct procedure. However, note that a 1065 code is specifically about the sensor signal itself, so this step alone is unlikely to clear the fault if the sensor or its wiring is at fault.
- Do not open the boiler casing or touch internal components Gas Safe engineer
Everything beyond the steps above requires a Gas Safe registered engineer. The pressure sensor is mounted internally on the primary circuit. Accessing it means removing the boiler casing and working near live electrical terminals and pressurised water pipework. This must not be attempted by anyone who is not qualified. Doing so could be dangerous, will almost certainly void your warranty, and is a legal requirement under Gas Safe regulations.
- Engineer to inspect the sensor wiring and connector Gas Safe engineer
A Gas Safe engineer will remove the boiler casing, locate the pressure sensor, and check whether the wiring plug is fully seated. In many cases this is the entire repair — the connector is reseated, the boiler is reset, and the fault does not return. The engineer will also check the cable along its run for any signs of chafing or damage.
- Engineer to test and replace the pressure sensor if needed Gas Safe engineer
If the wiring connection is secure, the engineer will test the sensor electrically. A faulty sensor will be replaced with a compatible part. Worcester Bosch pressure sensors are widely available and the swap is usually straightforward, making this one of the less disruptive internal repairs.
- Engineer to investigate PCB if fault persists after sensor replacement Gas Safe engineer
Should the fault code remain after the sensor and wiring have been confirmed good, the PCB's sensor-reading circuit is the next area to investigate. PCB diagnosis and replacement is specialised work and represents the higher end of the repair cost for this fault.
- Call a Gas Safe registered engineer Gas Safe engineer
If your boiler has not recovered after the reset attempt, contact a Gas Safe registered engineer. Provide them with the fault code 1065 so they can bring the likely parts. You can verify any engineer's registration at gassaferegister.co.uk.
Parts you may need
- Worcester Bosch pressure sensor · from £25
- Sensor wiring harness / loom · from £35
- PCB (if required) · 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 £90–£220, depending on the underlying cause.
Frequently asked questions
Is fault code 1065 dangerous — do I need to stop using the boiler immediately?
The boiler will already have blocked itself from firing, so there is no ongoing risk from the boiler running unsafely. A pressure sensor fault does not involve a gas leak or combustion issue. That said, you should not attempt to override the block or repeatedly reset the boiler hoping it will stay on — address the underlying fault with an engineer.
Can I fix a Worcester Bosch 1065 fault myself?
Not safely. Although the fault sounds straightforward, resolving it requires opening the boiler casing and working with internal electrical connections and pressurised pipework. By law, internal boiler repairs must be carried out by a Gas Safe registered engineer. Attempting it yourself risks personal injury, water damage, and will invalidate your manufacturer warranty.
How much does it cost to fix a 1065 pressure sensor fault?
For most households this comes in between £90 and £220 all-in, covering one hour of labour plus the sensor part if needed. If the connector has simply come loose, you may pay just a call-out and labour charge with no parts cost. The main variables are your location — London and South East engineers tend to charge more — and whether the job is carried out in normal working hours. In the unlikely event the fault turns out to be a PCB failure rather than the sensor itself, costs can rise considerably higher; if that happens, it is worth comparing repair cost against a boiler replacement, especially on an older appliance.
Why does my boiler keep showing code 1065 after resetting?
If the code returns every time you reset, the underlying hardware fault has not been resolved — the reset simply clears the display temporarily. A persistent 1065 almost always means the sensor connection is intermittently losing contact, the sensor has fully failed, or there is a wiring fault. Each reset that results in the same code is a signal to stop resetting and call an engineer instead.
Will my boiler warranty cover a 1065 fault?
Worcester Bosch offer warranties of up to 12 years on some Greenstar models, provided the boiler is installed by an Accredited Installer and serviced annually by a Gas Safe engineer. If your boiler is within warranty and has been regularly maintained, contact Worcester Bosch directly before booking an independent engineer, as the repair may be covered at no cost to you.