Ideal boiler showing F4 in Oldbury? It usually means a fault with the flow thermistor, the sensor that reads water temperature. What to do next.
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Turn the boiler off at the switch, wait a minute, turn it back on and reset once.
Mention any shelving, boxing in or plumbing work near the boiler. A pulled lead is a common cause.
The sensor is inside the case. Testing it needs an engineer and a meter.
Tests the flow thermistor and its connections, then replaces whichever has failed.
A photo of F4 and the boiler label. Say whether it happened suddenly or came and went.
If F4 appears for a moment and then clears, a loose plug is more likely than a dead sensor. Note the times it shows. A pattern helps the engineer find it faster.
On many Ideal boilers, F4 means a fault with the flow thermistor. That is the sensor that measures how hot the water is as it leaves the boiler. With no sensible reading, the boiler will not run.
The sensor can fail, or its wire and plug can work loose. Less often, the circuit board is at fault. Your manual will confirm the meaning for your model.
Ideal combis are common in Oldbury flats and new-builds near the town centre, often in tight kitchen cupboards. Wiring in tight spaces can get pulled when shelves or pipework are moved.
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Learn more →No. The boiler stopped because it could not read the water temperature. If there is a smell of gas, go outside, do not flick any switches, and phone the National Gas Emergency number, 0800 111 999.
Thermistors are among the cheaper boiler parts. The visit is usually short.
Not once the faulty sensor or lead is replaced.
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