Glow-worm F11, F12, F13 & F14 Boiler Fault Codes Explained

F11, F12, F13 & F14 Fault Codes on Glow-worm 24, 30, 38 CXI, HXI & SXI Boilers Explained


Glow-worm F11, F12, F13 & F14 fault code failure problems occur unfortunately, on a small number of 24, 30 & 38, CXI, HXI & SXI combi or system boilers. This is typically when they get to about 10 years old or older.

At Glowcare (being Glow-worm’s service agent for the North West of England since 1992), we do come across our fair share of F11, F12, F13 & F14 fault code issues, occurring within the Glow-worm CXI, HXI & SXI boiler model range.

These Glow-worm combi and system boiler fault error code problems typically come to our attention with a customer contacting us and explaining that their boiler has failed and can’t be reset. The fault code on the boiler’s digital display is flashing and is showing a F11, F12, F13 or F14 fault code. They go on to explain, that even though they’ve made many repeated attempts to reset the boiler by turning it off and on, the boiler will just not restart at all!

So, when the customer contacts us at Glowcare, their local Gas Safe installer may well have already attended the repair first, and established that there is 230 volts supply to the boiler and that the boiler’s gas and water pressures are all correct.
Establishing this, may lead the installer to conclude that there is nothing further that he or she can do to get the boiler working again, i.e. the boiler has gas and power, but there is still no heat or hot water and the boiler is just displaying either an F11, F12, F13 or F14 fault code.

The installer at this point will often judge that the customer will probably be best served by calling in an approved Glow-worm service agent, such as ourselves. Understanding that Glowcare, as Glow-worm agents, will be carrying at least 95% of any spare parts needed for repairs to the CXI, HXI or SXI with them, ensuring that the customer’s Glow-worm boiler gets expertly repaired and up and running in just one single visit.


Possible causes of the F11, F12, F13 & F14 fault error codes.


Glow-worm in their installation and service manual for the 24, 30 & 38, CXI, HXI & SXI, combi and system boilers, lists the following faults as:

Fault code of F11, the description says Main PCB, caused by a wiring problem between the User PCB and the Main board.

Fault code of F12, is described as User interface fault, caused by a wiring fault between the two User and Main PCBs.

Fault code of F13, this is described as a PCB (Main) connections fault, due to the wiring, or connections.

Fault code of F14, says the boiler’s Central Heating temperature on flow exceeds 95 degrees C, due to either a system fault, possible pump failure, or the thermistor needs to be checked on flow.

Looking at the four fault codes listed above, and taking the F11 fault error for example, it is of course possible, that the F11 fault lies within these wiring connections, between the User PCB and Main PCB board. All connections then, and the wiring block connectors on both of the two PCB boards, will need to be closely inspected and tested, to establish if the fault is on the wiring connections.

Work of this type can only be carried out by a Gas Safe registered engineer/installer, or a suitably qualified competent person, who is legally permitted to work on this type and model of Gas boiler.

However, it should be pointed out (as Glow-worm specialists), that there will be, in our experience, a good chance that the boiler’s main PCB may need to be replaced to resolve the problem with the F11 fault code!

The PCB, we find, usually causes the F11 fault and also can be the cause of additional fault codes F12, F13 & F14 on the CXI, HXI & SXI boilers as well.

Blank display screen failure, on CXI, HXI & SXI boilers, can result after F11, F12, F13 or F14, have been encountered.

Another related fault code display/PCB issue worth mentioning, and that our customers at Glowcare regularly contact us about (regarding their CXI, HXI or SXI), is that their boiler’s digital display is just rapidly flashing random numbers continuously, stuck in that mode all the time, and the boiler is obviously not working!


Glow-worm F11, F12, F13 and F14 Fault Codes, including blank display screen, for Glow-worm CXI, HXI and SXI Boilers.


Recently, one of our Glowcare customers contacted us, due to strange and unusual behaviour occurring with their 13 year old Glow worm 30 CXI boiler’s display, after returning home from a holiday. Prior to their holiday the boiler had been isolated (for safety reasons) and on return they turned it back on. The boiler’s display screen started stuttering, frantically displaying random numbers before going completely blank and “the boiler’s dead!”, no heating, no hot water.
Is your boiler experiencing the exact same issue?

Glowcare have always, and still advise customers to err on the side of caution, and make sure to turn off and isolate all Gas boilers when going away on holiday or vacation.

Sometimes when the boiler’s on-off knob/switch is turned off, the blank screen problem (caused by PCB failure) can occur, when the boiler is switched back on again. This very rarely happens but may still result in the PCB needing to be replaced.

An unfortunate failure of a CXI, HXI or SXI boiler’s PCB can happen at any time in the life of the boiler.

The failure that our customer experienced, is quite a rare occurrence, and safety we say must always comes first.

One Response to “Glow-worm F11, F12, F13 & F14 Boiler Fault Codes Explained”

  1. William Thomas

    My oiler is not running and displaying F13. been serviced regularly by British Gas until hi year. Changed organisation. Had an engineer visit. Supplied a quote to insurer with a Powerflush of £850 quote. Insurer does not cover powerflush so needs me to pay before anything else. So what is F13?

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