CH going off randomly

14 Aug 2005
Reaction score
United Kingdom
Hi All,

Boiler is Glowworm Fuelsaver 50R MkII, GC number 41 313 79.

The system works 90% of the time switching both HW and CH as required. However, on occasions, the central heating doesn't come on when programmed or the central heating comes on and then goes off despite what the programmer says. After a while, minutes or hours, it goes back to normal operation, till the next time.

I renewed the programmer as I wanted something more flexible and I suspected it might be the source of the problem. :rolleyes: You've guessed it, no improvement.

Any suggestions?


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thats a buugger

sorry but i would need to go at it mano a mano to find out what is the occurance

wait for chris or agile, and if he aint half cut ( ;) ) my old dad kev, they are better than me

just thought I would answer so you didnt feel lonely

nice aint i?

Could it be that your Room Stat is set too low?

For example if it is the dial type the dial may have slipped so the stat is set lower than you think.

What kind is it? Or indeed do you even have one?

Thanks for the company chaps.

No room thermostat fitted (yet).

The programmer always indicates what the situation should be i.e. CH light lit, but no heat at any rad until it resolves itself.

May be coincidence, but I think it may have gone off when the hot water kicked in.

Any help gratefully accepted.


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I'm so good I can answer this one easily.

I haven't a clue. See, that wasn't hard.
It means I can't remember anyone else's answer to copy into here to make me look a smartar5e.

Simple old boiler though, shouldn't be hard to diagnose if there with circuit diag and meter. Could be boiler stat I suppose.
Just in case it helps...

Even when the CH is not working properly, the HW works fine. Boiler fires up and heats water. Still no heat at the rads though.

There are two motorised valves under the floorboards, any chance they could cause this problem?



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