Worcester 28CDI Intermittent Air Pressure Fault

[MCW59]

I have a Worcester 28CDi, the exhaust fan was recently changed because it had had become noisy and had started to seize up.
At the time we were also getting Air Pressure Fault indications (flashing HW light).

Have been through the diagnosis in the book with CH engineer, cleaned sensing tubes out, checked flue OK, and changed pressure switch.
Still intermittent fault. When fault appears switch off at Control Panel, count to 10 switch on and boiler fires up OK. Will now probably keep going for rest of day. This happens once every couple of days. Worcester Tech. Advice line suggest new PCB, am OK with this if really at fault but at £175+fitting+vat could be an expensive mistake.

Any suggestions for a cure or do I have to spend the big bucks ?

 

[HarrogateGas]

For and extra tenner you can get WB out on a fixed price repair and it wont be your concern if it sorts it or not then.

 

[MCW59]

Thanks I'll certainly consider that.

 

[pannierstan]

My bets on the air pressure switch personnally. Have had loads and loads of em and it catches people out everytime.

If its the old brown APS then do it anyway but Ive had the white ones faulty aswell.

Stan

 

[MCW59]

Thanks for the info but the fault has gottenworse. The alarm flashes after 5-10 mins of use. On checking the exhaust fan still continues after the alrm indicates failure, then the pressure switch will drop out after the alarm not before. Still looks like the CB.

 

[Agile]

Be aware that the APS fault indication is ALSO caused by a low system water pressure on earlier ( most ) models.

Just to eliminate this possibility increase the pressure to about 1.7 Bar cold and see if this makes any difference to the fault frequency.

Tony

 

[MCW59]

Thanks, nobody from WB mentioned that before and the pressure is down about 1.2 cold at the moment.
I'll adjust it this evening when I get back home.

 

[Gilly10]

MCW59 and others - does this sort the problem out?

I have the same issue but thought that a pressure set to 1 was fine, will set the pressure to 1.7 tonight as well and see if that helps unless this is illadvised?

Annoyingly the fault only occurs on hot water and never seems to be caused by the hot tap - only the shower, when I'm in it!!! I have to then go and switch on/off the boiler to get it to reset....

 

[werewolf]

can you hear anything like relays chattering from pcb after being on for 5-10 mins..Had severeal go faulty on 24i range.

 

[Gilly10]

Have heard this once it's failed but not before... If it points to the PCB from what I've read it's best to get bosch in to do a repair fixed fee deal?

 

[clf-gas]

My bets on the air pressure switch personnally. Have had loads and loads of em and it catches people out everytime.

If its the old brown APS then do it anyway but Ive had the white ones faulty aswell.

Stan

I'll have a dollar on you stan, done one this afternoon same fault.
Fair point Tony, only this one was 1.5 cold.

 

[Gilly10]

OK upped the pressure from 1 to 1.5 cold last night - shower this morning cut out a few minutes in again... same problem...

considering changing the air switch and pipes but as the boiler actually starts up am I focussing on an incorrect area? Should I be focussing more on the heat exchanger/PCB?

 

[Gilly10]

Just noticed that the plastic fan on the fan assembly has broken away - last plumber I spoke to stated that the fan wouldn't make any difference.

Could this be causing a fault?

 

[nickso]

thats the cooling fan for the motor.....you will know when it makes a difference as the fan will be making nice grindy noises.

 

[jiminblack]

Had this phenomonon a few times. Have you checked the flue? No shrubs/trees covering it outside? Flue put together properly?