Intermittent central heating problem

[Bankrupt]

My central heating runs off an almost new Worcester Greenstar 42CD1 Combi Boiler but still uses my house's original Honeywell mechanical thermostat. It must be at least 30 years old by now, albeit its worked fine up to now.

Recently the central heating has sometimes been failing to start even though the thermostat contents should be "made".

Only two wires are connected to the thermostat. I've just done a quick test using a phase tester - I can see the voltage on the "downstream" contact change from mains voltage to a lower voltage as the thermostat contacts "break" and "make" which surprises me as I expected the "downstream" contact to have zero volts when the thermostat contacts were "broken"......

On the evidence so far, can anyone advise me if it looks like the symptoms suggest that I should try getting a new thermostat fitted ? - My suspicion is that the fault may be caused by the thermostat having become "dodgy" due to age. ( A bit like me )

Thanks.

 

[Agile]

Its unlikely to be the thermostat but its easy to bridge it out if you are unsure.

The correct way to test it is with a volt meter to earth.

I expect to be at the Castle Balti in Warwick tonight ( fri ) .

Tony

 

[bengasman]

My central heating runs off an almost new Worcester Greenstar 42CD1 Combi Boiler...

Call the installer. Any third party interference ( including diy ) may void the warrantee.

 

[jackecole]

you'd be better off with a nice new Honeywell wireless room stat ideally with a new boiler like that, but as said don't touch and get installer back. It could be a dodfy relay in the timer even.

You could try measuring (with power to system off) continuity between the contacts when the room stat makes and breaks.

 

[Bankrupt]

There's no timer involved - The only timer is on the boiler, and that was set to be continuously on.

I've now resolved the issue : The problem was the thermostat as I suspected.

Old thermostat replaced with a new Honeywell analogue thermostat ( can't see what the point of using a wireless thermostat for my application would be - The thermostat is on the wall in my living room which is the only room (apart from my wet room) where the radiators don't have thermostatic valves - What benefit would I get from installing a wireless thermostat ) and all is now well. .

Thanks for all your posts. .