Glow worm gas valve pulsating

28 Dec 2006
Reaction score
United Kingdom
Hi all. I\\\'ve got a glow worm fuel saver 45F. Having problems with the gas valve. Basically when the boiler fires up the gas valve opens as it should and ignites. The only problem is the gas valve continuously tries to open and close at the speed of light.
From what i have tested the voltage is fluctuating which is causing this. It doesn\\\'t happen all the time it fires up but does several times a week.
A plumber looked at it and and changed the gas valve but now says its an electrical problem, which would make sense.
Would the problem be the circuit board in the boiler. I can\\\'t think what else it would be.
Thanks for any help.
Chad :rolleyes:
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If a voltage is fluctuating when it shouldn't be, that is an electrical problem, isn't it?
So why change the gas valve? I hope the dork who changed it, set it up properly.

The mains signal which goes to the GV goes through a relay on the pcb and a couple of switches - all of which need testing by someone competent.
Ever seen one put in backwards? I do believe I uttered an expletive when the penny dropped.
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Ok well i hope i'm kinda competent i'm an electrician. lol.
I'm also going off info i've been given, as its a mates boiler.
Anyway, I had a feeling it was a relay on the pcb. What other switches are there to test? To be honest my experience with fault finding on boilers is very little.
If i were to replace the pcb this would cure the fault. Right??
Thanks Chad :confused:
Only maybe.
You need the manual - or the ability to follow a wire... ;)
Oh I see technical stuff. lol.
I have no manual and have already traced cables from gas valve to the pcb. From there its just a circuit board. I can't see any other switches! What sort of switches?? Help...
The pcb doesn't create the mains, it gets it from external ...switches! Check everything for your varying voltages
Ok well as always when i try to fix the fault it decides not to exist till a few days later when i'm not ready to fix it.
I'm concerned about the overheat cut-off switch on the boiler, as when you push the switch there doesn't seem to be anything there. Is this normal? (i'm not sure if this only is used when boiler over heats) :?:
As far as i can see all other switches seem to be ok.
I'm still thinking its the relay on the PCB.
Can anyone advise anymore?
Thank Chad :confused:
I am sure that it would be easy for a competent boiler engineer ( not a plumber ) in front of the boiler but from the information given there are so many possibilities.

My advice is not to get involved. Dont you have enough electrical work to do that you are experienced with?

I'm concerned about the overheat cut-off switch on the boiler, as when you push the switch there doesn't seem to be anything there. Is this normal?
Yes, normal. Often rattly.

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