Glow Worm 30cxi will not switch heating on/off with timer

[Phil R]

Hello folks. I have a 12-year-old Glow Worm 30cxi combi powering hot water and central heating. The analogue timer clock packed up recently and would not fire up the central heating either. Assuming it to be a fault with the clock, I got a second hand replacement and fitted it. Clock keeps perfect time, but the heating will not come on or go off on the timer. Hot water is fine and the heating works perfectly ok if you turn it fully on.

Over the years we have had replacement 3-way valves, PCB, etc., and I am worried that this is yet another expensive fault that has nothing to do with the clock! No fault numbers come on though. Has anyone come across this and know what the fault is please?

I've noticed form various forums that some people advise fitting a Programmable Room Thermostat in place of the room thermostat (in my case Honeywell T6360B) and leaving the boiler permanently on and being controlled by the PRT which seems sensible as our heating works happily when fully 'on' rather than on the timer on the boiler.

If this does get round whatever the fault is with the clock timer on the boiler, can anyone recommend the best one to work with the Glow Worm 30cxi please? I've had a look inside the Honeywell and it appears to have conventional wiring (blue wire to 2, brown-sleeved yellow to 3 and red to 1 - also earth to earth).

Your suggestions would be most welcome?

many thanks,

 

[Riley]

I would say likelihood is the clock but the pcbs have an annoying habit of crying on these for no reason. You shouldn’t be taking the cover off the boiler anyway so time to get a gse out to take a look

 

[Harvest Fields]

I would say likelihood is the clock but the pcbs have an annoying habit of crying on these for no reason. You shouldn’t be taking the cover off the boiler anyway so time to get a gse out to take a look

The outer case of fine mate. The inner is a definite NO NO

 

[Riley]

I just don’t like to encourage any

 

[Phil R]

That’s cool, folks, thanks. I will admit to swapping the timer clock over having still got the installation instructions from 2006 as my wife keeps everything like that! And I did help the engineer who came out several times to fit new 3-way valve, heat exchanger and pcb a couple of years ago, holding the torch for him as he cursed boiler designers who hide everything in the most awkward places and don’t think of the poor blighters who have to come out years later to maintain the things! I am on his side as I have the same problem in my day job!!

Just going to look up wiring up a replacement PRT for my existing room stat as this looks to be the best solution, in effect by-passing the clock timer on the boiler. I suspect the pcb is ignoring the clock, as you suggest and a new clock probably won’t solve it. In any case, for £150 a throw I would want it to make me a cup of tea in the mornings as well!

Many thanks again for sharing your expertise and experience - and I love the picture of the bear!