Glow worm Flexicom 30cx that displays the F9 fault code.

Billy66 · 3 Aug 2011

I have a Glow worm Flexicom 30cx that displays the F9 fault when switched on with no hot water / heating demands. It makes a few clicking noises but faults out after about 30 seconds .The manual says the pressure sensor or wiring or pump is seized. The pressure sensor reading is OK and varies if water is drained, flashing and disabling below 0.5 bar but ok at above. The pump is not seized. Can anyone help before I start replacing parts-- Thanks

misterdubya · 3 Aug 2011

Thats an error code you do not want so see.

Fan, pump, wiring, PCB, Pressure Sensor. O/Heat Stat. Some of it is RGI territory I'm afraid.

The last time I called Glowworm over that, it was an error code they had never seen. I had to literally re-build the boiler (apart from the heat ex).

DM46 will know more.

mickyg · 3 Aug 2011

does the pump actually spin? I would check impellor for blockages, check the return filter and rubber hose if it has one (depends on age). When you drain the boiler does the pressure sensor drop to 0? or 0.3? if it sits on 0.3 the sensor is faulty.

gasgeezer · 5 Aug 2011

Possiblle flat expansion vessel may need recharging,this can give F9 fault.

Agile · 6 Aug 2011

Is this F9 code triggered by a lack of change of pressure when the pump starts like the Vaillant F75 ?

If not then what does trigger it?

mickyg · 6 Aug 2011

Agile said:
Is this F9 code triggered by a lack of change of pressure when the pump starts like the Vaillant F75 ?

If not then what does trigger it?

yes that and other things. Combination of F75 and F22 basically

Andygasman2010 · 7 Aug 2011

I've had a nightmare with this F9 before too! Ended up being the DHW flow switch in my case but GW tech said, basically, it can be anything on the low voltage side!

Billy66 · 8 Aug 2011

Thanks for all your help, I've since found the pump does not turn when pcb puts mains on to it on switch on ( windings gone ). Found a pump head replacement awaiting delivery. Out of interest, why is the pump spun on initial switch on with no heating / hot water demand. Is it a routine or a pre-heat cycle ?

mickyg · 9 Aug 2011

just routine self check. Fan and pump both run on power up. Lots of modern boilers do it.

gricks · 15 Nov 2012

same symptoms as Billy66. Glowworm manual could be better written as Fault Finding Code F9 just says "Water pressure sensor fault - Faulty sensor connection, Check wiring". Was able to raise the pressure from 1.0 BAR to 1.2 BAR so the pressure sensor seemed fine.
Something sounded rough; fan was replaced and overheat trip needed manual resetting and boiler working again. Bank balance now £288 less (half the cost of this boiler ten years ago) but it has now 11 to 12 months insurance for other faults and parts through Valiant.

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Glow worm Flexicom 30cx that displays the F9 fault code.

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