glow worm compact 100e problem

[invictus]

Hi there
Looking for a little advice with my combi boiler problem before i dive in and start diagnosing
I`ve recently switched the boiler to `summer mode` and although it`s happened a couple of times intermittently, last night it became a permanent problem. When turning on the hot water tap the hot water would kick in and deliver the water as required and then shut off as soon as i turned the tap off. However,now the the pump is coming on and just cycling endlessly and not shutting off after i`ve turned off the tap !! I`m forced to actually switch the boiler off to stop it.
Has anyone experienced a similar problem and could they offer me any help with diagnosis ?
Any info would be much appreciated.
Thanks
Alex

 

[St0rmer66]

Could it just be pump over-run? It keeps the pump running (burner still goes off obviously) until the boiler has cooled down.

 

[invictus]

Sadly no. The pump would run on for hours if i left it.
I decided to have a look at the low water pressure switch to see if this was calling the pump in. After removing the switch i found the connector into the flow absolutely solid with rock hard sediment ( can`t believe how it`s been working) cleaned all this out until the water pressure operated the spindle and hey presto the pump doesn`t kick in anymore.
But now a new problem has arisen and i`ve now got a permanent low pressure light on and the boiler won`t reset because of this. When i operate the pressure switch microswitch, the contactors on the PCB pull in but the boiler state does`nt alter ?? I`m just about to bite the bullet and shell out £200 for a new PCB without being really sure that this will solve the problem.
Wish me luck

 

[St0rmer66]

From memory only here but... Do these boilers even have a low pressure switch? Isn't it just a 'pump proving' /flow switch? Which won't make if there is no pressure as the pump won't be pushing enough water. If so, it could be that you've unstuck the spindle from being permanently out now and it's seized permanently *in* instead. Or the diaphragm has perished sufficiently that it can't push it back out.

I think replacing the PCB at this stage is very premature that's all.

 

[St0rmer66]

Actually, re-reading what you've said... You're saying the pump coming on now DOES move the spindle? And have you tried manually pressing the micro switch once this happens? If it won't reset at all then it could be as simple as the button not pressing or last resort as you say.... PCB. Expensive mistake if it turns out not to be though as you won't be able to return it.

 

[invictus]

Sorry about my earlier post regarding the pressure switch. I did in fact mean the DHW micro switch. Again i removed the switch and had a look at the diaphragm and plunger, both are ok and move freely. Removed the microswitch and operated by hand which appeared to work ok as i could hear the switch making, so decided to get a new PCB purely on the basis that there was a `hot spot` on it when running and some light charring.
.
Fitted the board and everything worked fine, so feeling very clever with myself, i packed up for the night. However, i awoke this morning, turned on the hot water tap and the boiler locked out after a few seconds
I again i reset the boiler and dropped down the control panel. By chance i touched the cables to the microswitch and with the HW tap running it kicked in properly ??
I`m gonna check the switch for continuity as it appears it could be down to the switch after all.
Will update

 

[St0rmer66]

That spot always seems to get hot and burn out eventually. Usually results in low gas pressure to the burner which can't be adjusted any higher. I do hope you are capable of doing all safety checks after replacing the PCB... Especially since the ignition and burner pressures rely on correct setting up of the potentiometers on the board.

 

[Agile]

Another example of a DIYer carrying out gas work namely changing a PCB which needs gas adjustments on commissioning.

Not helped by inappropriate advice being given to encourage him.

Hearing a microswitch click does not mean its electrically connecting.

The discolouration on the PCB is normal on that model.

Tony

 

[bazdaman]

Plus the DHW microswitch is very unreliable on these did you try to link out?

 

[gas112]

A crap boiler that throws up to many red herrings on fault diagnosis and best repaired on fixed price from BG or manufacturer