Worcester Heatslave 14-19 not firing up

[johnmc008]

Hi all,

my 10 yr old heatslave has stopped firing up with no prior signs of problems. the over heat thermostat has not tripped out, no lock out, no problems with CH/hot water diversion. annually serviced and clean burning at last service according to flue gas analysis. had all the baffles out - all looking very clean for the age.

whether i demand CH, HW or both, it activates the pump but the boiler does not fire up.

i've opened two rad bleed valves at the top of the boiler - no air.

Then I opened the schrader valve on the expansion tank - and got a face full of high pressure water!! Presumably this is bad news. Could this alone be preventing the boiler from firing up?

this next part is a separate ongoing issue, probably unrelated but included just incase it's relevant: despite a clean flue & baffles, fine sooty deposit does occur in the boiler room. a couple of cracks in the insulated flue have been sealed but the problem persists.

as i write this, something about dirty windows & LDRs enters my brain....but that's lockout isn't it?

any suggestions gratefully received. unfortunately my expert oil oftec chap is off the radar at the moment....todays random pick from yellow pages scratched his head & said "you'll have to get worcester in", suggesting a PCB failure.

 

[dcawkwell]

Better luck with the next oftec engineer. Oil boilers are straightforward
to fault find. Goodness knows what he does on a gas boiler.
Did he not even think to ring worcester up and they would
guide him through a few checks to isolate the problem.

First thing to check is does the boiler have 240 volts to it?
If so and there is demand the next check would be is there 240v getting
to the burner control unit and then to the motor.
My guess would be the burner control, motor failure, faulty photocell

Oil boilers are very reliable.

Oh your expansion vessel has failed and needs replacing.

Low water pressure fault?

 

[oilhead]

Basic fault finding is to follow the path and check intermediate stages for voltage. Could be faulty limit stat even though it has not popped, or control box.

 

[Boilerman2]

Or the electrical plug for the burner has fallen out of it's socket under the control panel!!

Nice to hear that OHECK are still churning out Numpties!!

 

[johnmc008]

Thanks all for your suggestions.
High water pressure (although pressure guage is stuck..)
Perforated expansion tank full of water
No loose/failed connections as far as I can tell.
Voltage to pump & divertor working correctly.
No voltage being sent down to the burner from the pcb

new pcb? £80?

 

[Burnerman]

These have a pretty basic pcb, (£120 or thereabouts) but its worth removing it and checking for any burnt tracks before splashing out.
Bridge the overheat stat and see if that enlivens things?
PCB and EV's available from heating-parts.co.uk. and other outlets.
John

 

[johnmc008]

Discovered i had mains feed to the thermostatic cut out, but no output voltage despite the switch not being triggered. i shorted across the thermostatic cut out to feed the burner ignition and it fired up. bizarely when i removed the temporary short, everything worked as it should!

if it goes again, i'll have to replace the thermostatic cut out.

thaanks for your advice - problem solved (for now).