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Andrew Smith
Andrew Smith, Home Appliance Technician
Category: Appliance
Satisfied Customers: 3632
Experience:  Gas cooker specialist
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Plumberpro I have a Worcester bosch 28si II boiler. in coming home tonight I found th

Customer Question

Hi Plumberpro
I have a Worcester bosch 28si II boiler.
in coming home tonight I found the warning led flashing 5 times a second.
I reset by holding the button for 5ish seconds and it cleared the warning light.
I then went to run the hot water which worked fine for 2 minutes then went cold.
checked the boiler light is flashing again (5 times a second).
reset again but this time no woosh or spark, neither the hot water or the central heating is working and the led flashing yet again.
any ideas would be gratefully appreciated thanks
Submitted: 2 years ago.
Category: Appliance
Expert:  Andrew Smith replied 2 years ago.
Do you have the age or GC no.?
Customer: replied 2 years ago.
age I am unsure off but must 7 or 8 years old now
as for GC number its showing two for some reason
G20 47 311 67 & G31 47 311 68
Expert:  Andrew Smith replied 2 years ago.
Ending 68 is the LPG modelIt sounds like the fan is not running, can you confirm it is making the normal start up noises or remove the case to see if the fan is spinning?
Customer: replied 2 years ago.
ok removed the cover and when the hot water is turned on the fan spins for 1/8th of a turn and stops.
nothing else then happens until I turn off the water, at which point the fan spins up and rotates for a couple of minutes before all then goes quite and the fan stops.
I am on natural gas here so I assume it will be the one ending 67
Expert:  Andrew Smith replied 2 years ago.
What happens when you turn on the heating?
Customer: replied 2 years ago.
when turning on the heating the fan tries to spin for a moment / 1/8th of a turn then nothing.
sat waiting and nothing else happened until the light started flashing rapidly 5 times a second.
Expert:  Andrew Smith replied 2 years ago.
Are you able to check the fan tubing and the air pressure switch to make sure it is clean and working?
Customer: replied 2 years ago.
I have already taken off the fan assemble and all is clear and spins very freely by hand.
the two tubes a white and a red both look clear which I assume go to the air pressure switch.
unsure how to check the air pressure switch itself
Expert:  Andrew Smith replied 2 years ago.
If you put the tubes back on while the power is off.Blow/suck lightly on the tubes, one will click when you blow, the other will click when you suck.We need to make sure it does and then when the fan runs it should do the same.
Customer: replied 2 years ago.
yes both tubes click when I blow one and then suck the other
Expert:  Andrew Smith replied 2 years ago.
Ok, connect the fan again and see if it clicks when the fan runs
Customer: replied 2 years ago.
as stated earlier
ok removed the cover and when the hot water is turned on the fan spins for 1/8th of a turn and stops.
nothing else then happens until I turn off the water, at which point the fan spins up and rotates for a couple of minutes before all then goes quite and the fan stops.But this time as the fan spun up I did hear a click sound form the air pressure sensor
Expert:  Andrew Smith replied 2 years ago.
Ok, that's not good.The APS reports straight to the PCB, if the APS is clicking then I suggest the PCB needs replacing.Here is a link to the manual to check;http://www.acwilgar.co.uk/Boiler-Manual-PDF/Worcester%20Bosch/Worcester-Bosch%2024SI%2028SI.pdf
Customer: replied 2 years ago.
so the only option I have now is to try a new pcb in the boiler and see if that fixes the problem
Expert:  Andrew Smith replied 2 years ago.

It is expensive.

It may be worth an engineer standing in front of the boiler with a meter tracing the fault first?

Try the link first to see if you can narrow down the fault