Glow Worm boiler just always on!

[solidpro]

Hi Everyone

I've got a quite old Glow Worm Ultimate 80FF. It recently had an issue with the control stat (lots of green corrosion on it which was causing it not to come on) and I fitted a new one and I'm back in business. Everything was fine for a few days and now it's just always on.

We have two wired boxes on the wall in the house - central heating and hot water. After changing the stat, I could go to the thermostat on the wall switch it on and hear the boiler firing up, then off and it would go off. I did this a number of times and it was good. Now, it's just on all the time.

I've recently swapped the PCB (I have two) and no change. I've also recently replaced the overheat thermostat too.

I've tried unplugging both of the control boxes - and it still just fires up when you switch on the isolator switch. I can't figure out why it things it should be on.

You do have 4 lights on the boiler showing something like on, ignition, burn and it just goes through the sequence like I have the thermostat set to 30 degrees.....

What could be telling it to go 'on'??!

Thanks

 

[solidpro]

I did a bit of googling and some people saying a leaky tap or dripping rad could cause it. I did find a small radiator close to the boiler in a hallway that does look like it's dripping (hasn't been switched on until recently). I closed the valve and the boiler immediately turned off. Not sure if that was a coincedence!?

Why would a drip on a radiator cause the boiler to be on all the time?

Thanks

 

[Aquarius]

Failed motorised valve.

 

[solidpro]

Failed motorised valve.

That's what i've been told elsewhere.... i've found the two valves - one going into the hot water cylinder and the other presumably for radiators.... we're doing a test now waiting for the hot water to come on at 4.30 and see if the central heating comes on with it....

 

[Brambles]

Disconnect the external controls - see what the boiler does. Then bridge the control switch. If the boiler then performs, you know where to investigate further to find the fault.

If the boiler fails to perform when bridged then call in a gas safe engineer

 

[solidpro]

Hi - I found the fault. There are two actuator valves next to the hot water cylinder and I could hear that the hot water one was clicking and turning when the hot water was turned on an off, but the actuator for the central heating wasn't doing anything. I checked it had power and then isolated it and unscrewed it. The spigot on the pipe turned freely with my finger so it was a failed actuator. I took the model number off the external metal plate and found a guy 3 miles from me selling a brand new one on ebay! I went and got it and an hour later I had a fitted working actuator.

I re-tested the hot water and it does not turn the central heating on and then I tested the central heating and it comes on when called for from the controller in the hallway and turns off when it should.

I don't quite understand how the failed actuator means the central heating was on all the time (as they are closed when not powered) but I did get some help from another forum for carefully listening to these actuators coming on and off and that did seem to be the issue.

cheers