unable to repressurise combi boiler

[John Simpson]

Hi
I have a Worcester 24cdi combi boiler installed 3 yrs ago by a plumber in the loft above the flat. There have been no probs till yesterday when we woke to no hot water or CH. The boiler hums and the light next to the picture of the tap (on the front) flashes fast. This means blocked flue or fresha air supply says the manual. I cant get into the flue which comes out under the guttering and is inaccessible.
Is there anything else i can do...?
AND another thing....
The pressure is about 0.5 bars (although the plumber has left the red needle - the desirable pressure set even lower at 0.3 - can this be right?) So I put in the white plastic tap underneath and turned anticlockwise with no result - including no sound of filling which I ve heard in another boiler (in aprevious flat) - we also have no sign of leaks.
Is this a water supply prob or is there another explanation?
Id be grateful for all of your thoughts as we are pretty cold and cranky just now. Thanks

 

[kevplumb]

So I put in the white plastic tap underneath and turned anticlockwise with no result - including no sound of filling which I ve heard in another boiler (in aprevious flat) - we also have no sign of leaks.

you turn the grey knob as well

 

[John Simpson]

you turn the grey knob as well [/quote]

kevplumb - a great suggestion!-the system pressure quickly got to 1 bar

I pressed the reset button; the flashing light was gone
but....
still no HW or CH tho the relevant lights came on - then the cursed light (next to the pic of the tap) started its rapid flashing again.

I looked at the flue (from the back garden) where it vents thru the wall and could see no obstruction. It has a slotted cover on it so nothing could really get inside - how can it be blocked - yet this what this flashing light is sposed to mean according to the manual.

Has anyone got any idea where i go from here.
Thanks again to kev - certainly sorted the pressure

 

[ChrisR]

From the manual:
DHW Light Flashes Fast
Air Pressure Fault or Blocked Flue or Water Pressure Fault

Spot the difference?
Your water pressure switch has stuck in the off position. Usually that's because they block.
WHat pressure have you set it to?
If you put it a bit higher, say 2 bar, it might force its way though and start working after a while.

 

[HarrogateGas]

From the manual:
DHW Light Flashes Fast
Air Pressure Fault or Blocked Flue or Water Pressure Fault

Spot the difference?
Your water pressure switch has stuck in the off position. Usually that's because they block.
WHat pressure have you set it to?
If you put it a bit higher, say 2 bar, it might force its way though and start working after a while.

Last time I checked the CDi doesnt have a low water pressure switch.

 

[corgiman]

try turning the mains off and on again to zero up the board

 

[Mr Smyth]

Had one of these a while back with same fault.
Dis-connected the negative APS tube and blew through it. This cleared a minor obstruction and got the boiler working. When I returned the next day with the APS the boiler had lasted most of the day but had failed just before i got there. Changed the APS and everything OK.
Nothing to do with water pressure

 

[John Simpson]

Had one of these a while back with same fault.
Dis-connected the negative APS tube and blew through it. This cleared a minor obstruction and got the boiler working. When I returned the next day with the APS the boiler had lasted most of the day but had failed just before i got there. Changed the APS and everything OK.
Nothing to do with water pressure

Hi
Thanks to everyone for their time and suggestions but sadly still no joy with a) switching off at mains or b)boosting the water pressure to 2 bars. At first the rapid flashing light no longer flashes a fan starts (I feel hopeful at this point) then the light starts flashing again and the fan stops. The burner doesnt light.
So I'd like to try Mr Smyth's suggestion (Uzbekistan?!) as above
....but...
what is the APS, where is it, and how do I take it off (in order to do the blowing thru you mention)
praps someone can give me some pointers on this one
thanks again

 

[corgiman]

can you hear the fan going?

 

[gavinda]

ive had the aav inside leak on these before. the water tracks down and drips straight into the aps tubes. had this on friday funnily enough. close the aav for now until you can replace it and clear the aps tubes

maybe

 

[kevplumb]

APS is next to the gas valve if you drop the front disc shaped bit on a bracket

if you blow only blow down the tubes or you might well cream cracker the switch

looks a bit like this prob different colour tho

 

[John Simpson]

hi guys

thanks again for all the help and ideas
finally it was corgiman who picked it with his chance remark
'can you hear the fan'
which kind of fits with what the manual said about the rapid flashing DFW light being due to a 'blocked flue'

Indeed looking at the fan, it was immobile and on prodding it with the screwdriver, the electormagnet grabbed it so clearly it should've been going. Took the fan off, very stiff action, white stains - oiled the bearing - works!
Put it back on and hoopla - the house warms up and the crankiness slowly dissipates.

Can I say that we DIYers are engaged in a long and lonely guerilla struggle against the forces of darkness and cold but when you regular soldiers of home maintenance lend a hand we know we are fighting a common enemy and even when we are looking for a screw dropped in the half light of a freezing loft WE ARE NOT ALONE