Potterton Suprima 40 - Intermitent Problem

[smorgan851228]

Three and a half year old boiler which tends to turn itself off for no reason and requires frequent resetting.

A typical day - I have to reset the boiler each night before going to bed and after the timer has switched the system off - 11pm. 6am and the timer switches the system on, red light on permanently but green starts to flash as the system requires heat, fan comes on and 7-10 seconds later the boiler ignites. Boiler stays and after about 20 mins of it being on a buzzing sound is heard from below where the lights are for about 10 seconds. Varying amounts of minutes then pass and the boiler switches itself onto red flashing - off. Press reset button, boiler fires up and once heats water and rads up switches itself off, pump still running green light flashing slowly with red light on, green light flashes, fan comes on, sparky inside boiler starts sparking but buzzing sound from boiler for about 5 seconds - no ignition, boiler tries this three times and unsets itself. We have to reset it, but you can reset it after half a minute and it fires up with no buzzing sound at the first attempt. This goes on about 6-7 times a day and our plumber seems to think that its either the overheating thermostat, the sparker, gas valve or pcb! I only want to replace one bit, not all of them or else I might as well buy a new boiler by the time I pay for labour and vat!!!

Anybody with any ideas or same problem?

 

[ollski]

smorgan this is probably one of the best documented subjects on this forum a search will probably give you the answer you are looking for or I could just say the word pcb.

 

[smorgan851228]

My gut feeling is that it is the gas valve but it is so intermittent. I am fairly handy with tools - do you think that I would be able to change the pcb myself?

 

[doitall]

is your plumber corgy registered, then its a straight forward follow the fault chart with a tester.

does the red light stay on.

Thermistor, temperature control or board, all can be checked before renewing, should take 10mins

 

[smorgan851228]

yes sometimes the red light stays on which I beleive means that its working ok. However, every now and again it flashes and it needs to be reset to work again.

when you mean tester, do you mean a multi meter?

 

[smorgan851228]

where can I get a fault chart from? what do tyou check for - the resistance?

 

[doitall]

you didn't answer my question is the plumber corgy registered.

with your muliti meter and the power turned off, are the 2 yellow wires on the thermistor shorted.

with the power still off turn the stat up to max, are the 2 orange wire to the temperaturue control shorted.

are the 2 white wires to the temperature control shorted

 

[ChrisR]

Check to see if there's smoke coming out..

 

[doitall]

Check to see if there's smoke coming out..

Thats on the screwfix forum

 

[smorgan851228]

yes the plumber is corgi registered, should he have known about the testing etc?

 

[doitall]

yes the plumber is corgi registered, should he have known about the testing etc?

don't forget to post the result of the test and we should be able to tell which part to replace.

 

[smorgan851228]

2 yellow thermistor wires fine
2 orange wires fine
2 white wires fine

However, tested the eloctrode lead and found that the multimeter couldnt complete the circuit. Are there any metal wires in this lead or is it some form of synthetic conducting material. Odd thing is that once boiler put back together, it sparked ok and lit up anyway!!?? Any ideas what this might mean?

What next?

 

[ChrisR]

Check to see if there's smoke coming out..


Thats on the screwfix forum

Must be right then.

 

[fitz1]

check wires and plugs are not being displaced from the pcb. due to vibration. u may find boiler works fine whilst control panel is lowered.as soon as u push it back into place it pushes against boiler parts.i think it is this boiler that does it.

 

[doitall]

2 yellow thermistor wires fine
2 orange wires fine
2 white wires fine

However, tested the eloctrode lead and found that the multimeter couldnt complete the circuit. Are there any metal wires in this lead or is it some form of synthetic conducting material. Odd thing is that once boiler put back together, it sparked ok and lit up anyway!!?? Any ideas what this might mean?

What next?

are they open circuits or shorted, fine was not the question