Worcester 24i strange fault

[malkie]

I need some advice on a worcester 24 i fault please lads. It is standard 24i now what happens is for c/h and h/water it goes through its sequence it starts to spark and then it dosent ignite,now i was thinking gas valve but if i blow down the aps tube it starts to spark then fires up every time and will stay on until you turn it off but it wont fire up itself but blow at aps and fires every time i changed the pcb only because i had one and its only a 10min job,obviousley i put the old one back on but what do you lads think.I rang technical and he said"ring me from the job"so i did but he was as stumped as i am,what way shall i go now?. Ive cleaned the tubes and venturi out its very strange

 

[Deleted member 105431]

faulty aps?

 

[robbo9002]

Alright mate, if you have cleaned the venturis I would be looking at the flue and checking for blockages, also make sure the fan is running as it should as if its running slow the APS won't make. There is obviously no fault with the ignition sequence if it is firing up when you make the APS manually, so that rules out the board and gas valve. Could also be a sticky APS which onlymakes when you are blowing quite hard through it.

 

[malkie]

Thanks lads,am i right in saying you cant link them aps out just to test? and i was thinking fan but it does seem to be running ok,i know you can never be 100% but it is a vertical flue and maybe a blockage as you say?

 

[Agile]

Did you ever check the flue?

Did you measure the pressure presented to the APS?

Tony

 

[robbo9002]

Yeah you can measure the pressure across the APS, and see what you are getting. As I said before any probs with the flue/fan etc may cause insufficient pressure to make the switch.Hope you are CORGI reg? as there could be an obvious fault that only a trained eng would spot, there is also the safety aspect.

 

[Gasguru]

Is the test cap still in place on top of the boiler?

 

[Agile]

You should have posted this in the Combustion Chamber where we can give you unfetterred advice.

You dont seen to be having very good luck at the moment do you.

Some might say that you should not be self employed without more experience of boiler fault finding and pressurising systems.

Tony

 

[malkie]

Gas guru good answer i was there for a good 45 min before i thought hang on is the cap on,but it was.I am doing this as a favour for a old lady i know and i am really trying to keep the cost to a minimum so to tell you the truth im taking a 24i out tomorrow and i was going to take it with me and just try the parts as the only thing wrong on this 24i coming out is they just want a condenser. I could try all the parts and still be stuck,do you think it could be a flue proplem?.I am corgi reg infact ive just been this morning to finish my theory paper,so thank god its 5 years before i have to go back. I have checked all the obvious things but it is odd that it does all the correct sequence and then sparks but no flame but blow at the aps and it sparks then ignites,what is the difference between me telling the aps to operate or the fan telling it which it is otherwise it wouldnt start sparking

 

[Agile]

I have checked all the obvious things but it is odd that it does all the correct sequence and then sparks but no flame but blow at the aps and it sparks then ignites,what is the difference between me telling the aps to operate or the fan telling it which it is otherwise it wouldnt start sparking

The difference is that you are blowing harder.

But as you have not bothered to measure the pressure available to operate the switch you dont know why!

Have you done the other check by measuring the pressure the APS required to operate?

Tony

 

[lagunaglen]

Aps first but also check the fan is spinning as it should be, run hot water next time you try blowing down aps tube and see if fan spins faster

 

[namsag]

The boiler should not start ignition sequence unless the air pressure switch is making.
Does it only start sparking after the fan starts initially or is it sparking before fan starts which we know it should not do

 

[malkie]

It has fan running then starts sparking and it seems to be running as it should be i mean it certainly isnt sluggish and if the fan was faulty it wouldnt open the aps to allow sparking and it doesnt start sparking until the fan has started

 

[Agile]

Have you measured the resistance of the NO and NC contacts on the APS?

Tony