Worcester 24i ignition probs

[Dockie]

Hi I working on a24! That the fan was faul and replaced the fan but on restart the boiler would igniighte then go out like the flame sensor is faulty but replaced that and checked the wiring for continuity! No fault there!
Then replaced pcb as described in handbook but boiler is still showing the same fault!

Can anybody help?

Cheers

 

[southcoastboile]

sounds like a bit of a nightmare, have you checked inlet/wp?

 

[Dockie]

Gas pressure and water and central heating pressure all as they should be!
Expansion vessel has also enought pressure!

 

[southcoastboile]

was it doing this before you replaced the fan then or was it not working at all?

 

[Dockie]

The fan was seized and it was just sitting silent with the pump running

 

[tweakyboy]

Does the boiler actually ignite the gas and then lock out or just attempt to light?

 

[Dockie]

It atemps to light burn for a few seconds then cuts out and just sits idol

 

[southcoastboile]

something to do with the incorrect air gas mixture mabee? flue not connected correctly? only other things i can realy think of, hope you sort it m8

 

[Dockie]

The boiler was workin fine before the fan failed! So I haven't changed anything that would affect mixtures ect.

 

[tweakyboy]

Can you see the flame via the viewing mirror?

 

[Dockie]

Yeah it's small and I have also checked with the cover off so to see if it contacting the flame sensor correctly

 

[Dockie]

Yeah it's at ignition pressure and goes out within about 5 secs I also checkered it with the cover off to see if the flame is contacting the sonsor correctly

 

[tweakyboy]

I assume by taking the cover off to see the flame its the old 24i not the Greenstar?

 

[Dockie]

Correct it the 24i rsf

 

[Dockie]

I'm a caravan engineer so I don't see many green stars!

 

[tweakyboy]

When it first starts up isburner pressure at 1mb?

 

[Dockie]

Not sure I've not noted the burner pressure at startup

 

[tweakyboy]

Check the burner pressure at start up, the M.I's say it should be 1mb for 60secs before modulating.

 

[Dockie]

But it's not continuing onto a continuous burn it is giving the symptoms of being the flame señor ie the spark is not stoping and then goes out but I can check the burner pressure tommorow! When I am back there. Do u think I could be the gas valve?

 

[tweakyboy]

Could possibly be a faulty gas valve, possible faulty solenoid on it.

 

[Dockie]

I will check that out! I thought it might be the valve but I wasn't sure! But the thing is why would it give the symptoms of being the flame sensor and not the valve. Would it be the flame is not hot enough to activate the sensor?

 

[tweakyboy]

Just a quick thought, you said your a caravan engineer so I assume your on LPG, so you should have 3.5mb instead.

 

[Dockie]

Yeah ur right I am on LPG! I thought 1mb was low!

 

[tweakyboy]

Another one to check if you switched the gas off whilst changing the fan via the isolation valve under the boiler make sure it did open fully and that there is nothing blocking it. You will still get your pressure at the gas valve even if its open a tiny bit.

 

[Dockie]

No that's not an issue as I didn't switch it off but I checked it was fully open when I started I have probs.