Potterton Puma 80 - Problem with boiler not turning off

[QTR]

Hi. I have an issue with my Potterton Puma 80 combi gas boiler and was wonderin whether anyone could help. Just recently it has developed a problem with the hot water and central heating. When I turn the the boiler switch on the boiler sparks up immediately and begins heating water, this is regardless of whether a hot water tap is on or not, or whether the central heating is on or not. If I do turn a hot water tap on then the boiler works fine, i.e. it produces hot water until I turn the tap off. At this point the boiler carries on heating the water on full flame, until after about 30 seconds it completely cuts out., blowing the pilot light out. At the moment I am having to turn the shower on, turn the boiler switch to on, using the shower, then turning the boiler switch to off before finally turning the shower off. This is the only way to keep it from putting the pilot light out each time I use it.

The main problem though is the CH. When I turn the boiler on, as above, it fires up straight away, regardless of whether the CH or DHW are on or not, therefore it soon overheats, even with the central heating drawing water, and continues to cut out.

The PCB is issue 5, there is no leaking water from the outflow pipe, the boiler is the old type (ie it has the pilot ignition button that sticks underneath the cover every time you press it in).

I have asked around and received various explanations, is this is common problem with a common solution or does it depend on other variables I am not giveing you information on?

Thanks for taking the time to look at this, I'd appreciate any help, if I need a new boiler then fair enough but I can't really afford one and would much prefer to fix this one for the time being and save for a new one.

Thanks again.

 

[Gasguru]

Flowswitch is stuck on. Pop off front panel and you'll find the red LED is on with the hot taps OFF. Replace the flowswitch.

 

[QTR]

Thanks for the help. I'm not very experienced in terms of plumbing and boilers, is replacing the flowswitch a relatively easy job or would I be better off getting someone in? Are they particular to makes of boiler or are they generic?

Thanks again.

 

[Gasguru]

You need the Potterton part. Flowsensor and microswitch are about £40 - £50.

For me its about the easiest boiler repair.

 

[QTR]

You were right, the red LED is on without the boiler switch even being turned on, and remains on the whole time. Can I perform a check to see whether it definitely is the flowswitch before i go ahead? Where is it located as I look into the boiler?

Thanks again.

 

[Gasguru]

See the images here

 

[QTR]

Legend!! Thanks Gasguru, I've just opened it up and given the flowswitch a few taps with the handle of my screwdriver, LED went off straight away, and now it is working perfectly, with both hot water and central heating. I'll keep an eye on it but at least we've got some heat for the time being and I know what's wrong with it now.

Cheers again.

Neil.

 

[QTR]

I spoke too soon it seems. It was working fine, however, now a different problem has arisen. The LED is off aqt all teh right times and the hot water works, but the CH is intermittent. i.e. when I turned it on I could hear the fan going but it didn't light up the boiler. When I turned the hot water on and off though it stayed lit if the CH was switch on Constant. Then after 30 secs it went off, after a further minute it came back on again of it's own volition. It seems to be turning itself on and off even though the thermostat is way over teh current temperature. I will monitor it over the next 24 hours but if this sounds like an additional problem I would appreciate your advice.

Many Thanks.

 

[Agile]

Either you have a dripping tap or a failing diverter valve!

If the water switch stuck once its likely to stick again!

Tony

 

[QTR]

Now working fine without making any changes, I think it just needed to cycle through the central heating programme. Thanks again.