Glow worm blowing fuses

[Akersstuff]

We have a Glow Worm Majorca 2 back boiler that we plan to replace in the summer (yes 30+ years old - but been ok so far) but as luck has it, the thing has stopped functioning because of blown fuses. The control circuitry to the boiler is ok. The boiler ignites, runs for a few minutes and then turns off due to the 500mA fuse blowing. I replaced the transformer - to no avail. tried the boiler thermostat at different temps but still the same. The only thing I'm left with is the solenoid gas valve but can this cause problems like this? Can you even get spares for this model anymore? We're cold (very cold) but do not want to spend anything much on this boiler as it will eventually go and we'd rather spend the dosh on a condensing boiler.

 

[ChrisR]

Dodgy thermostat is all I can think of. Unless there are any leaks making things wet. I don't know the circuit - what else is powered via the fuse ?

 

[Akersstuff]

Fuse goes to gas valve one side then the boiler thermostat the other. The thermostat connects to 24V off the transformer. Surely the thermostat is just a switch. Are there any tests I can easily do - I'm an electronic engineer?

 

[doitall]

have you checked the pump.

 

[Akersstuff]

The pump was the first thing I checked (before I realised it was the fuse that led to no heat). The pump is fully operational - water circulating. Pump starts working before boiler turns on so I don't think it's some sort of surge that's blowing the fuse.

I'll test the thermocouple/thermostat tomorrow just to put my mind at rest.

 

[ChrisR]

Gas valve coils are usually 2 - 4kohms
Yes the stat's just a switch, but they can start to fall apart or get conductive dirt in.

There's always the REAL ENGINEER's solution - put bigger fuses in - it'll either get better or show you where the fault really is by glowing red..

 

[Akersstuff]

At least if things start glowing red we'll have some HEAT!!!!
Thanks for the help Chris.