Ideal F7 fault codewhat it means and how to fix it
The mains voltage reaching the boiler has dropped below what the board will run on. Ideal's advice is an electrician or your electricity supplier, not a heating engineer.
Take care
What F7 means
F7 is Low Mains Voltage. The Logic's board monitors the supply and refuses to run the fan, pump and gas valve when the voltage sags, because low voltage makes the fan run slow, the gas valve chatter and the flame sensing unreliable — all things a boiler would rather not do with gas flowing. It is the only code in Ideal's user-guide table whose action is not the boiler at all: "Contact a qualified electrician or your electricity provider."
The Vogue manual gives the number the board is working to, less than 185 volts, and adds two follow-ups for the engineer — check whether a local generator is the supply, and if the mains measures fine, look at the pump and then the primary PCB, since a failing pump can drag the board's supply down from the inside. On a Combi2 the mirror-image code exists too: F 14 for a supply that is too high.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Poor supply into the property | Rural ends of long lines, shared supplies and evening peaks can all dip below 185 volts. Other appliances dimming or a flickering kettle light are the corroborating evidence. | Common |
| A loose or corroded connection in the boiler's own circuit | The fused spur, its 3 amp fuse holder and the terminal block behind the boiler can all develop resistance that drops the voltage only under load. | Common |
| Pump or PCB pulling the voltage down | Ideal's Vogue chart sends the engineer to the pump, then the primary PCB, when the incoming mains measures correctly. The fault is inside the boiler but shows as a supply code. | Occasional |
| Generator or inverter supply | Ideal single this out. A boiler run from a small generator during a power cut will frequently show F7 because the output droops the moment the pump starts. | Rare |
What to try yourself
Check the rest of the house. Lights dimming when the kettle goes on, or an oven clock that keeps resetting, points at the supply rather than the boiler, and that is a call to your electricity network operator on 105.
If everything else is normal, the fault is between the consumer unit and the board. Ideal's instruction is a qualified electrician; the fused spur and its connections are theirs to open, not yours.
Get a Gas Safe registered engineer to look at your Ideal F7
We do not pass enquiries to a repair firm, so there is no form here. Find a Gas Safe registered engineer through the Gas Safe Register, and ask to see their registration card when they arrive — it is the register, not the van, that tells you they are qualified.
What it costs to fix
Typical repair cost
£0–£300
Time on site
1 hour
Nothing if the network operator finds a supply fault, which they fix at no charge. An electrician's visit £80–£150; a pump or PCB if the fault is internal, £180–£300.
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
Parts you may need
We may earn a commission if you buy a part through one of these links. It does not change what you pay, and it does not affect which parts we list.
Central heating circulating pump
CH-PUMP-15-60£90–£180Plumbing merchant
Price checked 28 September 2026
Ideal Logic primary PCB
£150–£320Authorised Ideal parts distributor
Price checked 28 September 2026
Own this appliance and had this code? . Nothing is published until a person has read it.
Related Ideal fault codes
- F9Get it checkedThe control board has not been told what boiler it is in, or has failed. L9 is the same fault locked out. The 2011 Logic Combi row also covers a gas valve short circuit.Related: electronics and power
- dUUsually simple to fixNot a fault. The diverter valve has been parked in its mid-position for servicing and the boiler is waiting to be told the service is over. Ideal publish the way out.Related: electronics and power
- Blank displayGet it checkedNothing on the screen at all. Ideal's user guides send you to the boiler's switch and the consumer unit first; the installer charts then work from the terminal block to the board.Related: electronics and power
- C0Get it checkedThe board cannot activate the Boiler Chip Card that tells it what model it is fitted to. Ideal's engineer check is whether the small plastic card is in its slot at all.Related: electronics and power
- L9Get it checkedOn a Logic, L9 is the locked-out form of the unconfigured-board fault F9. On an Isar HE it is something else entirely: a heat exchanger overheat read by the dry-fire thermistor.Related: electronics and power
- SEUsually simple to fixA service reminder, not a fault. The installer set a timer at the last visit and it has run down. Ideal's advice is to contact the installer, who resets it when the boiler is serviced.Related: electronics and power
Own an Ideal boiler? Save it and its codes come first next time.
Related guides
Common questions about Ideal F7
Should I call a heating engineer or an electrician?
Ideal say electrician or electricity provider, and that is the right first call because in most cases the boiler is reporting the house, not itself. The exception is when the supply measures fine at the spur: at that point the Vogue chart goes to the pump and PCB, and that is a heating engineer's job.
Will the boiler restart on its own when the voltage recovers?
F7 is an F code, so yes, it clears when the condition does. A boiler that shows F7 every evening at six and runs again at eight is describing your street's load curve, and the network operator will want to know.
What is the difference from F14?
Direction. F 14 on a Logic Combi2 is High Mains Voltage, with the same instruction to contact the electricity provider. Older Logic boards only report the low side.
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer technical and service documentation
- Manufacturer support portal
This page has not been reviewed by an engineer, and we would rather tell you that than imply otherwise. The severity rating follows what the manufacturer publishes: where they say isolate the appliance and call someone, so do we.