Ideal Boiler F4 Fault Code
The Ideal fault code F4 flwo thermistor Q & A or require an engineer for an emergency boiler repair.
The Ideal Boiler Fault Code F4 Error Common Q & A
Just below, we have a list of common questions relating to the F4 fault code on the Ideal boiler.
- What does the Ideal F4 fault code mean on my boiler?
- What is the flow thermistor on my Ideal boiler?
- What can cause the F4 fault code to be displayed?
- Is my Ideal boiler dangerous if it’s showing the F4 fault code?
- Can loose and damaged connections on the flow thermistor be fixed?
- My boiler engineer says it’s the thermistor that’s faulty rather than the wiring/connections, what should I do?
- How much does it cost to replace the flow thermistor on an Ideal boiler?
- Why would the PCB be the cause of a thermistor related issue like the F4 fault?
- Why would the PCB malfunction on my Ideal boiler?
- How will my boiler engineer know if the PCB is broken?
- My boiler engineer thinks the PCB needs replacing, how much is this going to cost?
- What has the pump got to do with the F4 fault code?
- Why isn’t my pump pumping at a high enough speed?
- Can a blocked pump be fixed?
- My pump is broken, how much will a new one cost?
What does the Ideal F4 fault code mean on my boiler
If your Ideal boiler is showing the F4 fault code, there is a problem with the flow thermistor, or something related to the thermistor’s operation. These faults are also linked to circulation issues in the boiler.
What is the flow thermistor on my Ideal boiler
Your boiler has a thermistor on the flow and return pipe.
The flow pipe is the pipe on your boiler where heated water leaves the boiler to travel around the heating system.
The return pipe is the pipe that water comes through after travelling through radiators and towel rails, ready to be reheated.
Thermistors measure the temperature of water in and out of the boiler.
By monitoring the temperature of flow water, the thermistor can determine if the water is being heated. And even when it is, it can sense fluctuations in temperature that might mean there’s a problem with water circulating around the heating system.
The thermistor measures in resistance (ohms). This reading is sent to the printed circuit board (PCB) which then converts this into a temperature reading.
If this reading is out of tolerance (too hot or cold), the PCB will lock out the boiler and display a fault code, in this case that’s the F4 fault code you’re seeing.
What can cause the F4 fault code to be displayed
It’s important that you don’t work on your boiler unless you are Gas Safe registered.
A registered engineer will need to determine what the problem is, and this could be things such as:
- Loose or damaged connections
- Faulty flow thermistor
- Main PCB fault
- Pump failure leading to water circulation issues
- Incorrect installation
Is my Ideal boiler dangerous if it’s showing the F4 fault code
If your boiler has locked out and is showing the F4 fault code, it’s not dangerous.
The lock out you’re experiencing is a safety function. If the boiler continued to operate, there’s a chance it could be dangerous.
And that’s why we never advise people to reset their boiler when there is a fault code being displayed. The reset could temporarily fool the boiler into thinking the problem is fixed.
The fault should be found and fixed before the boiler is reset.
Can loose and damaged connections on the flow thermistor be fixed
Loose and damaged connections can be fixed to clear the F4 fault code on your Ideal boiler.
Most loose and damaged connections to the flow thermistor will be obvious to the naked eye, so a quick visual inspection will enable your boiler engineer to see what the problem is.
However, if there’s nothing that looks wrong visually, they’ll need to test the flow thermistor connections and wiring using a multi-meter.
If the wiring/connections are in extremely poor condition, it’s worth considering a replacement thermistor instead of reconditioning the wiring.
My boiler engineer says it’s the thermistor that’s faulty rather than the wiring/connections, what should I do
This is a simple case of replacing the component, if existing wiring/connections are in good condition.
How much does it cost to replace the flow thermistor on an Ideal boiler
Boiler repairs can be more than £500 in some instances.
Luckily, this isn’t one of those instances.
Flow thermistors for most boilers can be found for under £50. And with a few hours labour, it’s likely that the total cost of repairing your boiler by fitting a new thermistor, will be less than £150.
Why would the PCB be the cause of a thermistor related issue like the F4 fault
The PCB is the most important part of your boiler. All electrical components in the appliance need to communicate with the PCB in symphony for the boiler to continue to operate.
As a quick example, the boiler won’t fire unless the fan is recognised as running. That’s because the fan helps harmful gases get pushed out the flue.
The problem is if the boiler’s PCB is broken, it might not recognise the fan is running even when it is.
And the same thing could be said for the flow thermistor. The reading the PCB is getting might show the flow thermistor as logging a temperature that’s too high, even when that’s not the case.
In this case, replacing the thermistor won’t fix the problem as it’s the PCB that’s at fault.
Why would the PCB malfunction on my Ideal boiler
Old age is certainly a potential culprit. However, we find that in most cases, it’s actually water damage that’s caused a PCB to malfunction.
PCBs are designed to outlast a boiler, so it’s unusual that they’ll fail without a helping hand.
Unfortunately, there are components such as the heat exchanger and pump that can give this helping hand. These parts are prone to leaking.
When they do, they can leak over all the electrical components in your boiler, including the PCB.
Water damaged can burn out connections, wiring and eventually ruin the PCB completely.
How will my boiler engineer know if the PCB is broken
Like the tests they complete for the thermistor’s wiring and connections, the boiler engineer will be able to use a multi-meter to test the PCB, as well as the wiring/connections to the PCB.
In some cases, the issue might be something minor such as a loose connection that’s been caused by the boiler vibrating.
In a worst-case scenario, the boiler’s PCB will need to be replaced to clear the F4 fault code on your Ideal boiler.
My boiler engineer thinks the PCB needs replacing, how much is this going to cost
You should think carefully before replacing a PCB. The cost of a replacement could be around £500 depending on the exact boiler you have.
efore replacing a PCB, the boiler engineer needs to:
- Be certain the PCB is the issue
- Check all other expensive components in your boiler for signs of excessive wear
Generally, even an expensive £500 repair is worthwhile. However, if other components in your boiler are likely to need replacing soon, it’s probably a better idea to replace the boiler with a new and energy efficient one instead of repairing your old one.
What has the pump got to do with the F4 fault code
As we mentioned, the thermistor will monitor the temperature of heated water that’s leaving your boiler.
For it to circulate, it needs to be pumped. If it’s not being pumped quick enough that’s a circulation fault, and it’s likely the water leaving the flow pipe is too high in temperature.
Why isn’t my pump pumping at a high enough speed
The first thing a boiler engineer will need to check is that the speed setting is correct. Many newer pumps have up to three speed settings. Larger properties will use a higher speed setting, whereas the slowest speed setting is likely to be enough for small properties.
If the speed setting isn’t correct on your boiler’s pump, this can create a circulation problem.
Another possibility is that the pump is partially blocked. This could be trapped air, a worn pump shaft, or even heating sludge.
Like a low speed setting, if your pump has a blockage, it won’t be pumping correctly, and this will lead to a circulation fault.
Can a blocked pump be fixed
A boiler engineer should be able to fix a pump that’s blocked. They’ll remove it, take it apart and clean it. If the blockage hasn’t caused back-pressure that’s blown the pump seals, the pump should be in good enough condition to be re-used.
My pump is broken, how much will a new one cost
If the engineer has decided that the cause of the F4 fault code is the pump and that it needs replacing, you should expect to pay around £250.
The price will vary slightly depending on the size pump you need and the quality of the brand (Grundfos is recommended).
Other Ideal boiler issues
For more boiler issues regarding the Idea Boiler then please visit the Ideal Boiler Problems And Cures page.