Jaguar Combi Boiler F0 Error

This is a common fault on these boilers that I get called out to regularly. Customers think that there is a serious problem with the boiler and it requires an engineers attention. In reality the problem is usually caused by the pressure being too low in the central heating system.

The boiler contains a water pressure sensor which measures the pressure in the central heating system which will need to be topped up every now and again. How often it requires topping up will depend upon the system but may only be once a year. When cold the water pressure should be topped up to around 1.5 bar. If the water pressure drops to 0.5 bar or below the F0 error will be displayed and will occur if the system is drained or the pressure drops over time.

To top up you need to press the bar button which will show the current pressure in the central heating system. Then on the flexible filling loop which is usually fitted to the pipework below the boiler the cold water inlet valve needs to be opened. On the standard filling loop which came with the boiler you will need a large-headed flat screwdriver or small adjustable spanner to open the valve. On a better quality filling loop it may have a washing machine style tap. Whilst the system is filling you may need to press the bar button again because the display will revert to the system temperature. Once the water pressure is up to 1.5 bar it is important to turn the filling loop fully off, ideally disconnecting the flexible pipe to ensure the system isn't overfilled. If you do put too much water in the system you will need to drain some out to avoid causing further problems.

As soon as the water pressure gets to 0.7 bar the F0 error will be cleared and the pump may start up to help clear any air out of the boiler. If the pressure drops regularly it may be due to a leak and further attention from an engineer may be required.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.