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Andrew Smith
Andrew Smith, Home Appliance Technician
Category: Appliance
Satisfied Customers: 3757
Experience:  Gas cooker specialist
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Our Potterton 30 HE lost pressure overnight and the burner

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Our Potterton 30 HE lost pressure overnight and the burner went out. I have topped the water back up to 2 bar aprox but am unable to reset it. Both red lights 30 & 50 are flashing and the burner will not come back on.
I have tried turning the stat on & off and leaving the hot water running but nothing happens.
I have power and the fuse is ok.
Can anyone help, the Boiler was installed 5 years ago.
***** ***** : Is there a reset position on the main selector switch?
***** ***** : 30 and 50 degress will have another symbol also - what are they?

Yes there is a reset on the main selector switch, which I have tried by rotating to the left for two seconds as indicated in the instructions. I have done this with success on several occassions before.


The 30 degrees is the burner/ignition light (which is not lit at the minute)


The 50 degrees is some sort of fan symbol?

***** ***** : Ok, it is telling you that the boiler does not know the fan is running - can you confirm this?
***** ***** : Try holding the control knob at the reset position for over 6 seconds and see if it springs back into life?

I have tried that the boiler looks like it is going to start initially but the two lights 30 & 50 start to flash and the boiler doesnt light. I have tried this several times previously? There is a fan/pump type noise coming from within the boiler?

***** ***** : We need to know if the fan is running?
***** ***** : If the fan is running then it could be an air pressure switch fault
***** ***** : If the fan is not running then it could be a fan fault
***** ***** : Are you willing to take the outer case off to start with?
***** ***** : But we will need to expose the fan which is another cover also

Yes, I am an electrician,the pump is running i need to find the fan then?

***** ***** : inside the case at the top near the flue


***** ***** :
***** ***** : Page 48 onwards if you have a meter

The fan is not running

***** ***** : Do you have power to the fan?
***** ***** : Will it start with a push and some WD40?

There is no power to the fan

***** ***** : Can you check that the APS clicks when you blow into it.
***** ***** : Are you able to follow the fault finding guide I sent you?



Yeah i can follow the guide

***** ***** : Air Pressure Switch, this tells the boiler that the fan is running, it could be stuck 'made'

There are two blue cables going to the flue at the top of the boiler will that be the APS

***** ***** : Page 47 - blue, black and brown

I can see it but am unable to blow into it, it is in the top right hand corner behind the fan. I have tried tapping it?


Top left corner not right?

***** ***** : Can you take the hose off the fan and blow into it lightly?

Which one the clear one or the black one?

***** ***** : one will be a blow and the other a suck

I blew into the clear one and the APS clicks ok

***** ***** : Ok, you need to put a meter across it like manual syas and check it is switching electrically

I have no power to it?


Apart from the mains I only have power (230V) to terminals 5 & 6 on A4.


Is it not the PCB that needs replacing, that was my initial thought this morning?


Is that it now you're not coming back online I take it?


Please reply?


Term A2 - across 5 & 7 no power, replace PCB


Term A2 across 1 & 2 overheat stat shorted out, replace PCB?

***** ***** : No power to any connection on the APS to earth?
***** ***** : No power to the fan, each connection to earth?

No power to all

***** ***** : It looks like the PCB is at fault, but just need to prove it
***** ***** : Is the pump running?
***** ***** : If the pump is running, it could be the primary flow switch

The pumps is running as previously mentioned and I have carried out the checks mentioned above?

***** ***** : The primary flow switch fires the boiler once the pump is running

Term A2 - across 5 & 7 no power, replace PCB

2:52 PM

Term A2 across 1 & 2 overheat stat shorted out, replace PCB?

***** ***** : Can you see if it is lifting?

How do I see if it is lifting, I assume you mean the primary flow switch?


Where is the primary flow switch?

***** ***** : 2 red wires iI think

Yeah it closes then brakes when i turn the power off

***** ***** : ok can you disconnet the wires and see if it 'makes' with a meter when the pump runs?

there is 12v across the cables when the pump is running and nothing when it isn't


You keep leaving all the time


Get back to me please

***** ***** : Continuity please. not voltage

Yeah it is closed

***** ***** : So it makes when the pump runs, or it is made all the time?

As above it is closed when the pump is running?

***** ***** : and breas when the pump turns off?
***** ***** : *breaks

Yes as above it is open when the pump is off

***** ***** : ok, we have rules out everything that should fire the boiler, but it doesn't.
***** ***** : Sorry this has taken so long, but I needed to prove everything else was working fine before suggesting a new PBC
***** ***** : but I think we are at that stage

Ok thanks that confirms what I thought initially i just wanted to speak with somebody with Boiler knowledge before i bought a new PCB.


Thanks for your time.

***** ***** : Have a look around and make sure you are buying a new one - not a reconditioned
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