Valliant Combi Boiler - error code F24 (plus other probs!)

[LollyPopStar]

Can anyone help me - or shed light on the mysterious workings of my Valliant boiler?

We have a Valliant Combi boiler - installed new in 2002. No idea the model no as I can't see a sticker or code anywhere!

But it has been playing up for the past 2 to 3 years. Mostly by not producing hot water consistently. i.e you get in the shower and the water is hot but it will suddenly go cold, then hot again. Green light flashes but no yellow heating light.
Sometimes it doesn't ever get hot - and we have to resort to turning boiler off and on again, or my fave trick is to turn the heating on while I need some water
.
We did get round the original installer to have a look, but as the problem is only intermittent, the boiler of course behaved perfectly when he examined the damn thing and he couldn't find anything wrong!

So we've kind of been living with it (with me muttering that I will take a hammer to the boiler if I have one more stressful shower..!)
Anyway this winter the boiler has presented us with a new form of devilry. The F24 code.
It appears usually in the mornings on the LCD screen and there is no heating or power.
We can usually get round this by turning the system off and on again but this morning it turned the heating on but we could get no hot water (although apparently its started working again now)
We've got someone from Valiant supposedly coming round on Wed - charging £200 just for the call out.

But I really don't want *him* to find nothing wrong and walk away. Can anyone arm me with information as to what the problem could be before then - so I can get him to check EVERYTHING.

Thanks in advance!

Laura

 

[Agile]

Probably an 824 or 828 variant.

I dont know about F24 but the book lists normal codes. Trouble is there are other codes as well.

On another make I recently encountered an unlisted fault code. I had a good laugh with the manufacturer when it was listed on the latest documents as "other faults" !

By aware that there are three common faults on your model which could be present in single or multiple combinations.

1. Diverter sometimes fails to move, can give heating instead of hot water.

2. APS sometimes fails to operate and boiler may not fire up.

3. Hot water heat exchanger may be partially blocked by dirt from a system that has not been properly treated.

Tony

 

[pierrot]

8) It smells suspiciously like the diverter valve, these were going faulty literally within weeks of install at about that time, had you called out vailant under the guarantee they would have changed it. Its such a common fault that your local branch of HRPC will more than likely have the part on the shelf.

 

[ricardo111]

THE F.24 FAULT CODE IS GENERATED WHEN THE RISE IN TEPERATURE BETWEEN THE TWO `NTC` SENSORS IS TOO FAST A GRADIENT (USUALLY). THE PCB TRANSLATES THIS INFORMATION AS `NO WATER IN BOILER`, AND LOCKS IT OUT WITH F.24, CAUSING YOU TO PRESS RESET. IT MAY THEN WORK FOR SOME TIME. UNSCREW THE NTC`S AND CHECK BEHIND THEM FOR MOISTURE-THIS CAN CAUSE F.24, OR LOOSE NTC`S NOT SCREWED FULLY HOME INTO THE SOCKET.
ANOTHER CAUSE OF F.24 IS LOW WATER PRESSURE - THE GAUGE SHOULD READ 1.5 BAR WHEN THE HEATING IS OFF/COOLED.
ANOTHER CAUSE OF F.24 IS THE PUMP INTERMITTENTLY STICKING, IS THERE A LOT OF SLUDGE IN THE CH SYSTEM-THIS CAN STICK THE PUMP CAUSING F.24
ANOTHER CAUSE OF F.24 IS A FAULTING PCB, REPLACE WITH NEW ONE PART REF 130806, BUT MAKE SURE THE GAS VALVE JUMPER IS SET CORRECTLY- RIGHT TWO PINS FOR A S.I.T VALVE, LEFT TWO PINS FOR A HONEYWELL GAS VALVE.
THE INTERMITTENT LIGHTING/NOT LIGHTING PARTICULARLY WHEN YOU RUN THE TAP IS A DUFF AIR PRESSURE SWITCH- VERY COMMON FAULT.
YOU NEED TO REPLACE THAT. ALSO THERE IS A CHANCE THE DIVERTER VALVE IS STICKING IN HW/CH POSITION BUT I DOUBT THAT BECAUSE YOU SAID THE ORANGE LIGHT IS OFF (IGNITION) BUT THE GREEN ONE IS FLASHING(RUNNING TAP). HOPE THIS HELPS.

 

[ollski]

I don't really come across many vaillants, but the few I have come across round here on the green / white models with the fault self diagnosis have been the air pressure switch. Have a look in the manual on how to get into the fault checking codes, then check the aps...see if it is turning on and off.

 

[LollyPopStar]

Top marks to the Vaillant engineer - he took one look at the boiler and said "Yeah these lot all had faulty air pressure switches - should have been fixed under warranty"
He checked said air pressure switch - found it was grey and said that was the culprit - I obviously needed a black one.
Got one out of the van and it was fixed in 5 minutes!

And he didn't charge me - what a sweetheart!

Anyway guys n gals thanks for all your posts

Laura

 

[saw0304]

I noticed one of my hall radiators needed bled yesterday and on doing so seemed to have messed up my Vallaint boiler. There is an F20 error code and the red light has come on indicating that there is no pilot light on in the boiler. Does anyone know if there is anything I can do to rectify this problem? There is no manual for the boiler and like others have said I can't see any details to inform me of the model name. I don't have a clue what the four circular bottons do - one has an image of a flame with a cross over it which I presume is something to do with the pilot, but the others don't have any obvious image to give me a clue.

Help! Could really do without a callout charge just before Christmas!
Stephen

 

[mehran]

On another make I recently encountered an unlisted fault code. I had a good laugh with the manufacturer when it was listed on the latest documents as "other faults" !

it was not a biasi by any chance?

 

[MichaelFISH]

Hey, I have a Vaillant Thermoblock turboTEC II that my plummer has given up on. He has exchanged almost everything. It is still unable to restart and goes on F.24 or (if I ask for hot water and centralheating) it will go on forever (two bad things for a heater - never start and never stop - I am looking for the opposite).
Then I found Ricardo111's answer: THE F.24 FAULT CODE IS GENERATED WHEN THE RISE IN TEPERATURE BETWEEN THE TWO `NTC` SENSORS IS TOO FAST A GRADIENT (USUALLY). THE PCB TRANSLATES THIS INFORMATION AS `NO WATER IN BOILER`, AND LOCKS IT OUT WITH F.24, CAUSING YOU TO PRESS RESET. IT MAY THEN WORK FOR SOME TIME. UNSCREW THE NTC`S AND CHECK BEHIND THEM FOR MOISTURE-THIS CAN CAUSE F.24, OR LOOSE NTC`S NOT SCREWED FULLY HOME INTO THE SOCKET.
Dear Ricardo111 (or anyone else) - my plummer says this is an uption, and he knows what NTC is. But can I do this myself and remove moist?

 

[ricardo111]

Hi MichaelFISH - regarding your f.24 plus other faults.
Here in UK we don`t have a `thermobloc turbotec II` but I have been told by my old employer (Vaillant) it is the same boiler as a Turbomax Plus here in UK.
You can unscrew the NTC`s to check for moisture, they are screwed into a dry pocket so you dont need to drain the boiler or anything. However if boiler is more than a few years old, it is unlikely that moisture behind the NTCs would cause this now, it was usually within the first few months of use and due to no thermal paste applied at the factory during manufacture.
I have cured intermittent F24 fault by replacing main heat exchanger- some corrosion build-up/sludge in there can cause the ntc`s/PCB to detect too rapid a heat rise and lead to intermittent lockout F24.
OR, I do remember being told to renew the PCB as a last resort, Vaillant had discovered that the program was too sensitive to the heat curve across the main heat exchanger, and they had the program altered on later PCB`s to account for the intermittent F24 faults we kept getting called back to, so you might want to change that, but check the gas valve jumper switch top left hand area of the PCB is identical as the one you take out! Can`t be certain on this one but I would change the main heat exchanger if I were you, and if your plumber uses a chemical like Kamco FX2 or similar he should also flush out the secondary `plate` heat exchanger. Take a look at the quality of the water drained from the boiler- let it settle in a clear glass - any sludge evident? Regarding the comment about you can`t turn it off once started - have you got the `pre-heat` activated? Pre-heat was a function you can turn on so the boiler fires itself up every hour or so to keep itself warm, ready for the next hot water demand. You`ll know if it is active by the green light being on constant (only flashes when tap is turned on). To de-activate this function, turn hot water thermostat fully anti-clockwise hold until green light goes out then turn back to desired temperature. It is activated by turning thermostat fully clockwise, and green light comes on. It might just be this occuring or if you really cant turn it off once it`s going, I would suggest the PCB is faulty. SO, a main heat exchanger and a PCB is the doctor`s prescription here. All the best, Rich

 

[jakbop]

F.24 Fault also occurs when automatic air vent malfunctions, for example if float lever is detached from valve inside cap.

 

[Bunnyman]

No it doesn't? An that threads 6 years old mate

 

[Steelmasons]

F.24 Fault also occurs when automatic air vent malfunctions, for example if float lever is detached from valve inside cap.

 

[jakbop]

No? Well, I wonder, can you be sure?
From Vaillant: F.24 Dry fire protection (temperature gradient of flow NTC too steep). Air in boiler/system, pump blocked or defective, pump output too low.
I seemed to have S.53 Delay mode due to lack of water in system (~20 mins.) kick in with the fault after about about 15 seconds on after firing up CH, which re-occurred - which is a check. Pump was fine, cleaned the NTC. Fault and S.53 re-occurred. Note Fault also declares air in boiler; Checked the system for air, and believe I could hear the air in boiler and it wasn't purging, so I checked the automatic air vent and finding the float lever detached from valve, reattached it. Boiler sprang to life without S.53, or F.24.

What do you think Bunnyman?

The thread's a day older, and so are all turbomax's (-: