Gloworm Ultimate 40FF Blows PCB Fuse

[Gillo]

Hello

I have searched through the old threads, but not been able to find an answer to this one. The Glow worm manual has not helped me with this one either.

On Sunday, our Gloworm Ultimate 40FF central heating boiler cut out and a short investigation revealed tha the switched live PCB fuse had blown. I replaced the fuse today, but it blew as soon as I turned the central heating on. It did not even have time for the fan to start before it blew. The boiler is as old as the house (8 years) and I flushed the central heating system 14 months ago when changing a radiator. We have lived here 2.5yrs and that is the only work that has been done since we moved in.

I suspect the pump or fan, but just wondered if these are the components I should be checking first?

Reading through the threads I know I should get the boiler serviced once I have sorted this issue out...

Any help would be much appreciated!

Dave

 

[corgiman]

is one with two fuses?

if so the pump dying will blow the one at the bottom

 

[ChrisR]

Disconnect the fan, the pump, the gas valve, and see if it still blows fuses.

Reconnect in what order you suspect..

I'd sniff the pump for smell of leaks or burning.

Last one I had was a roomstat, wet wallpaper paste...

 

[Gillo]

Yes it is the PCB with two fuses and it blows the fuse at the bottom of the board, labelled F1.

So it looks like a pump check would be my first port of call.

Thanks

Dave

 

[corgiman]

good luck

 

[Gillo]

Thanks guys. A nice task for tomorrow when I have been to Maplins to buy some more F1A fuses....

Dave

 

[ollski]

Thanks guys. A nice task for tomorrow when I have been to Maplins to buy some more F1A fuses....

Dave

I would buy one fuse and a multimeter

 

[corgiman]

or just a new pump

By the way oll how do you check a pump with a multi meter?

feel free to take the mick I just have never found the need and am interested?

 

[ollski]

Disconnect the wires and then just check the resistance across each of the windings, have the expected readings written on the mm if you want them.

 

[geoff@cetltd]

If there's tracking (e.g. because of water ingress or something) a multimeter won't necessarily show a fault that you woud see when mains is applied

 

[Gillo]

Well, when I disconnect the pump from the PCB, the fuse does not blow. I have checked the resistance across the pump and it reads 324ohms. Is this a normal reading? Either way, I suppose the next step is to replace the pump?

Thanks

Dave

 

[kier]

try this first.....gas valve could be the culprit.test by pulling gas valve lead off pcb,start ignition process you should hear fan running and electrode sparking.if fuse stays good confirm by reconnecting gas valve lead and if fuse blows its the gas valve.
ps work safely with electrics.

 

[Gillo]

Kier. Thanks for the reply. The PCB still blows the fuse when I disconnect the fan and gas valve (leaving the pump connected). When I connect the fan and gas valve, but disconnect the pump, the fuse does not blow so it seems to be something in the pump or its wiring. Its strange that the pump has not gone open circuit, but I suppose it could be seized or some water in the electrics (no sign of a leak though).

Thanks

Dave

 

[corgiman]

stop mucking around and replace it its knackered

As I believe I said ages ago

sheesh

 

[Gillo]

I have checked the pump (connected directly to mains with fused plug) and it works. And the pump also comes on if I turn the thermostat on the boiler off

Since then I have had a good look at the PCB (unbolted from its carrier) and underneath the circuit board I can see that it has burnt out. Is this likely to be the cause of my problem or just the symptom of another fault? New PCBs are ~£70 so I don't want to blow a new one straight away !

Thanks

Dave