Hi all, I am a GSR engineer and had a look at a worcester 28i junior combi today which keeps locking out (4 flashes every second) unsure if its the fan or PCB? Fan seems ok but 240v only being sent to it very briefly (approx 1-2 seconds) then it locks out again. I'm pretty positive its not the air pressure switch as it locks out far to quickly which I would say would also rule out the gas valve and spark generator as the ignition sequence isn't getting that far. does the PCB check resistances on all the components eg fan gas valve solenoid etc before anything or is it a component on the PCB or dry joint??

Rob, October 2009

hi fellow sufferers
woke up to find no dhw or ch.boiler red light flashing no flame led not lit.pressed red flashing light, boiler fan starts but no clicking [ignition noise]
had the relay problem[relay 1 blackened on pcb board]
the relay is connected to the fan in the flue, if you follow the wires from the fan they lead down to the relays.
if you turn the boiler off at the mains switch wait a few mins ,then also set the room thermostat controller to the clock symbol [constant setting]then switch power back on the fan should start up in the flue if it fails at this point to click [ignition spark sound] i have found a switch on the left-hand side of the bosch water pump a three speed switch set it to a different speed and have found the boiler lights and will heat up the CH for an hour or two ,a small mercy when its freezing cold.but have found out if you run CH and DHW it goes into lockout... but wait all is not lost wait 3 - 5 mins for the boiler to cool then repeat voila CH on for a few hours again.
ps going to turn CH off then run the DHW for a bath later,as it seems with this fault you cant' have CH+DHW at the same time.sorry no quick fix am going to have to buy new pcb

kawabunga, November 2010

hi mate i have a 28i and have been experiencing same locking out, i have had the pcb out and no signs of any dry joints, the fan is working fine i checked this by disconnecting power to the boiler and then setting CH to constant when you turn power back on the boiler fires up but no spark then fault light starts again. when i try again i noticed there was a noise missing as the boiler tryd firing ,a clink sound. found this to be pressure switch. on the top of boiler should be red valve cap,not the one on the expansion vessel the one on front left, i turned off gas supply and put a pipe on to it and created a vacum (sucked it was desperate at this point ) and the clink noise was back, still with gas off i powered the boiler and sucked pipe and it sparked. looking at pressure switch it appeared fine when i removed it, it had loose bits inside. i reassembled the switch but left disconnected the white pipe to the valve but left it connected at fan and top of boiler powered it again and it fired perfectly. briefly knowing fan and flue were working fine and re assembled boiler turned gas back on and worked fine. i have ordered a new switch by internet and am convinced this is at fault. if this fails i going to call out worcester as i believe they have diagnostic tool. hope this can help

chris, October 2009

fan relay on pcb is knackered, new pcb req. it's quite a common fault.

Ian, October 2009