Ideal F6 Fault Code: Causes, Fixes & Repair Costs
What does the Ideal F6 fault code mean?
The F6 fault code on Ideal boilers signals a problem with the outdoor temperature sensor. When this code appears, the boiler locks out as a safety measure and will not operate until the fault is resolved. The outdoor sensor is what allows the boiler to practise weather compensation — adjusting heat output based on how cold it is outside to maintain comfort and keep energy use in check. When the boiler stops receiving a valid signal from that sensor, either because the sensor has failed, wiring has been damaged, or there is a communication problem with the PCB, it displays F6 and shuts down. This code is seen across several Ideal boiler ranges including the Logic Max Combi, Logic Plus System, and Logic Plus Regular.
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
- Faulty or failed outdoor temperature sensor Common
The outdoor sensor itself has developed a fault, either due to age, moisture ingress, or physical damage. This is the most frequent cause of F6 on Ideal boilers. The sensor can drift out of its expected resistance range, causing the boiler to detect an implausible reading and lock out.
- Damaged or loose sensor wiring Common
The cable running from the outdoor sensor back to the boiler can be pinched, chafed, or corroded — particularly where it passes through an external wall. A poor or loose connection at either end produces intermittent or out-of-range readings that trigger the fault.
- Sensor incorrectly installed or positioned Sometimes
If the outdoor sensor has recently been fitted or moved, it may have been wired incorrectly or sited in a location that gives an unrepresentative temperature reading — for example, in direct sunlight or too close to an air vent. The boiler then interprets the reading as a fault.
- PCB fault or communication error Rare
In a smaller number of cases the PCB itself is unable to interpret the sensor signal correctly, even when the sensor and wiring test as healthy. This is typically only diagnosed after a sensor and wiring check has ruled out the more common causes.
How to fix it
- Reset the boiler once DIY safe
Turn the boiler off using its controls, wait about 30 seconds, then power it back on and attempt a reset following the instructions in your Ideal boiler manual (usually holding the reset button for a few seconds). If the F6 code clears and does not return, monitor the boiler over the next day or two. Do not reset more than once or twice — repeated resets without resolving the underlying cause are not safe and can mask the problem.
- Check whether an outdoor sensor is actually fitted DIY safe
Look for a small sensor unit mounted on an outside wall, usually on a north-facing elevation away from direct sunlight. If you cannot locate one, it is possible the boiler settings have been configured to expect a sensor that was never connected, or a sensor was fitted but has since come loose. Note what you find to pass on to the engineer.
- Inspect the sensor wiring for obvious damage DIY safe
Trace the cable from the outdoor sensor to where it enters the building. Look for visible signs of damage such as cuts, heavy kinking, or signs of pest activity. Do not disconnect or reconnect any wiring yourself — simply note anything unusual so the engineer can investigate further.
- Contact the original installer if recently fitted DIY safe
If an outdoor sensor was installed within the past few weeks, get in touch with the installer and describe the F6 fault. An installation error — such as reversed wiring or incorrect sensor pairing — is a straightforward fix for the original engineer and may be covered under their workmanship guarantee.
- Call a Gas Safe registered engineer to diagnose and repair Gas Safe engineer
If resetting the boiler does not clear the fault, or if it returns after clearing, a Gas Safe registered engineer needs to attend. They will test the sensor's resistance values against Ideal's specifications, check the wiring continuity, and inspect the PCB. In most cases this results in an outdoor sensor replacement, which is a relatively quick and affordable repair. If the PCB is found to be at fault, they will advise on the cost and viability of replacement versus a new boiler.
Parts you may need
- Outdoor temperature sensor (NTC) · from £25
- Sensor wiring harness / extension cable · from £18
- PCB (control board) · from £260
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 £100–£280, depending on the underlying cause.
Frequently asked questions
Can I use my Ideal boiler without an outdoor sensor connected?
Yes, in many cases it is possible for a Gas Safe engineer to disable the weather compensation function in the boiler's settings so it runs without an outdoor sensor. This means you lose the efficiency benefits of weather compensation, but the boiler will operate normally. Whether this is the right long-term solution depends on your system setup — your engineer can advise.
How long does it take to fix an F6 fault?
If the fault is a failed outdoor sensor or a simple wiring issue, a qualified engineer can usually diagnose and fix the problem in a single visit of around one to two hours. If the PCB turns out to be faulty, the engineer may need to order the part, meaning a second visit is required.
My Ideal boiler keeps showing F6 even after being reset — what should I do?
A fault that returns after resetting almost always means the underlying component problem has not been fixed. Stop resetting the boiler and arrange for a Gas Safe registered engineer to carry out a proper diagnosis. Repeated resets will not resolve sensor or wiring faults and can mask warning signs.
Could an F6 fault mean I need a new PCB — and how much does that cost?
It is possible but relatively uncommon. A PCB replacement on an Ideal boiler typically costs £200–£400 including labour, depending on the specific model. However, an engineer will always test the sensor and wiring first, since these are far more likely to be the cause and are much cheaper to replace. If your boiler is over ten years old and the PCB has failed, your engineer may suggest that a new boiler is a more cost-effective option than an expensive PCB repair.