Fault on worcster 28i

[davyboy10]

Hi Guys, just joined this forum and so here goes. I am a corgi registered engineer and have recently started to repair combis of all types and names.

So the question I want to ask is, I was called out to a worscter 28i after a contractor had fitted an outside water meter. So I automatically assummed there would be debirs on the cold inlet which was restrciting the flow switch. But after checking the boiler I found it was neither working on the hot water or heating and the customer is adamant the boiler was fine before the installation of the water meter.

So here's what happens the boiler goes to fire up, the pump starts, the fan starts, the aps makes the switch and then there is nothing no spark nothing. I put my multimeter on the 2 pins of the gas valve connection on the PCB and there was no reading. Does this indicate a fault with the PCB if there is no voltage from the PCB to the gas valve or have I missed something. There was no manual with the boiler so I was going off experience. Any help or advice would be appreciated before I buy a PCB.
Dave

 

[Paul Barker]

Good you have proved the aps,

testing gas valve won't establish what's wrong when the problem is no spark. I don't know the test for the spark, it's at very high voltage. I would say make sure route to electrode is free of shorts and that ceramic part isn't broken just like you do on a manual spark igniter. Clean electrode tip, check gap.

If still no spark phone Worcester they may say is there such and such at so and so pin on pcb.

 

[B.O.B DOLE]

have you checked the spark genertator

 

[davyboy10]

I haven't checked the spark generator because I assummed you would need voltage at the pins of the gas valve from the Pcb after the pcb has been proved and the spark generator works in tandem with that, or is the sequence after the aps switch has been proved that the spark generator should be going initially before voltage at the pins of the pcb.
Dave

 

[B.O.B DOLE]

I haven't checked the spark generator because I assummed you would need voltage at the pins of the gas valve from the Pcb after the pcb has been proved and the spark generator works in tandem with that, or is the sequence after the aps switch has been proved that the spark generator should be going initially before voltage at the pins of the pcb.
Dave

just looked at manu,s and have you checked conti on the ignition cables if they are ok it says replace control board,

 

[geoff@cetltd]

I haven't checked the spark generator because I assummed you would need voltage at the pins of the gas valve from the Pcb after the pcb has been proved and the spark generator works in tandem with that, or is the sequence after the aps switch has been proved that the spark generator should be going initially before voltage at the pins of the pcb.
Dave

The gas valve gets its power from a relay on the pcb

For the sequence to have got that far, thew pcb has to have seen a demand for heat. Have you actually measured the resistance of the c-n/o contacts on the APS? and are you sure the wiring is intact to the pcb

If so, you're running out of options other than the pcb

 

[davyboy10]

I haven't checked the spark generator because I assummed you would need voltage at the pins of the gas valve from the Pcb after the pcb has been proved and the spark generator works in tandem with that, or is the sequence after the aps switch has been proved that the spark generator should be going initially before voltage at the pins of the pcb.
Dave

just looked at manu,s and have you checked conti on the ignition cables if they are ok it says replace control board,

Thanks for that, I was thinking the same thing but needed a second opinion. I used to have all the worscter manuals but lent them to someone and never got them back. I know that a lot of the worcster's have to go through a certain sequence before firing up. I went onto the worcster site to downl;oad the technical. fault finding information but It wasn't there, just the user manuals and the installation one, thanks again.
Dave

 

[jiminblack]

Sounds like a PCB. Same symptoms. Repaired one today. Part number 87161463290...it's still written on the back of my hand!!

 

[Agile]

Last ditch attempt! I suppose that you have not overlooked any overheat stat?

Customers always like to blame someone else for their boiler's faults.

Some would even get a water meter fitted just because they think they will get a free boiler repair thrown in!

Tony

 

[davyboy10]

Hi Guys, well I fixed the problem today and as I suspected it was the PCB but thanks for all your input it was very helpful. I have only just joined this forum and already finding it has many benefits for engineers like me in the field so keep up the good work.
Dave