Viessmann F2 Fault Code – Likely Causes, And Possible Fixes

October 17, 2022

What Is the Viessmann F2 Fault?

The F2 error code is another that relates to temperature.

Unlike F0 and F1, the F2 fault is a bit more specific as it points to circulation rather than overheating.

Your Viessmann boiler will monitor the temperature of both the flow and return pipes, if the gap between these two pipes is too large or increases too quickly your Viessmann boiler will register that there is a circulation problem and shut the boiler down until the temperature difference has reduced.


Common Causes of The F2 Fault

The most common cause of this fault code is a faulty pump. The pump is responsible for circulating water from the boiler around the heating system. If it malfunctions, the water will heat rapidly in the heat exchanger and the boiler will lockout.

Another common cause of the F2 fault is a corroded, or blocked heating system. If you have never had your system cleaned, it’s very likely that overtime the radiators have corroded on the inside.

This corrosion will eventually gather and restrict the flow of water around the heating system, causing your Viessmann boiler to display the F2 fault.

Other relatively common causes are airlocks, that restrict the flow of water. And a faulty PCB not sending power to the pump.


If I Reset My Boiler, Will This Fix the F2 Fault?

After sufficient time has passed and the temperature difference between the flow and return has reduced, resetting your boiler will temporarily clear the F2 fault code.

Although the fault will clear, the boiler will probably still not work.

As the Viessmann F2 fault is usually caused by the pump either seizing, or due to the PCB not sending power, after the boiler has run through its ignition sequence your Viessmann boiler will quickly lockout out again to the F2 fault.

Similarly, if your system is severely blocked and the flow of water is restricted, the temperature of the flow and return pipes will increase too quickly and your boiler will again lockout with the F2 fault code.


Can I Fix the F2 Fault Myself?

As the F2 fault will probably be due to a faulty pump, you will need to call a Gas Safe registered heating company to carry out a proper diagnosis and boiler repair.

If the fault is due to a blocked heating system, then a proper powerflush will be needed, and if the main heat exchanger is completely blocked you might decide it is more cost effective to simply get a new boiler as the cost for a main heat exchanger can be quite expensive.

If after resetting your boiler it works for a while, then goes to a F2 error after a couple of days you might want to check for air in your radiators before calling a gas engineer.

For more things to check before calling a gas engineer, click here.



The F2 error code is a strong indication that there is an underlying fault with your heating system. If the pump has failed, it’s often due to a poorly maintained boiler and heating system. An adequate and routine boiler service will help you to spot any problems with the heating system, before they cause issues and result in a breakdown.

The fault will eventually reset, but only temporarily until the reason for the fault is properly diagnosed and repaired.

Heatsy are Viessmann trained, DBS cleared, and Trading Standard approved heating contractors. We specialise in domestic heating boiler repairs, Gas Safe number 648547.

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