Worcester 35CDi pressure problem

[Freddie100]

Hi, I have a Worcester 35CDi combi, about 8 years old, which has a fault that is gradually getting worse. The DHW demand LED flashes quickly, and the boiler won't light.

Sometimes it was just when starting up in the morning, but over the last month or so it now does it during the day, I think when hot water is used.

When it cuts out, the pressure gauge shows zero. Feeding a little more water into the system and raising the pressure to around 0.25 bar makes the fault clear, and the boiler lights straight away. Later the pressure reads 2 bar.

I know from the manual that the HW LED flashing quickly indicates either an air pressure fault, blocked flue, or water pressure fault.

I took the covers off and found that the air pressure switch had cracked near its mountings, and was lying loose inside! I've just fitted a new one, but the problem is still happening.

The flue is a short horizontal run (1 metre); no pipes seem to be leaking anywhere.

Any advice on what to check next would be much appreciated...!

 

[REDSAW]

hi welcome to the forum.
could this be the diverter? hmmm!

 

[miajanjua]

Your expansion vessel is in need of replacement.

 

[fireblade]

2 problems realy expansion vessel pre charge and on the boiler there is a multiplug at the bottom on the left side it is all the wiring from the water pressure switch over heat stat fan wires and air pressure switch just unplug and crimp the little tubes on the connector slightly plug back in and should be fixed i know this after finding this fault after speaking to worcester and fitting a new board and it making no difference

 

[wes]

did you said that the water pressure in the manometer rise up?
and later is down to cero?
them put a new expansion vessel.the red big thing rectangular o round one it could be grey depent.