Digistat SCR needs replacing?

1 Oct 2013
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United Kingdom

My boiler is not working.

Setup: Vaillant combi boiler, with a digistat scr near it and a room control thermostat in another room. The thermostat had a little flame symbol indicating it was asking the boiler to fire, but nothing was going on.

I didn't understand why but noticed that the scr wasn't showing any lights of any kind (my impression is that it's supposed to flash red multiple time every few minutes to indicate it is getting a signal). The scr seems to be a fairly standard one (iflo digistat), which looks a lot like the drayton, and has buttons labelled 1 and 2 (override). I pushed override and nothing. Then I pushed 1 and nothing. I pushed both together and nothing.

After fiddling for a bit by turning the mains to the scr and boiler off, the scr magically came back to life... for a day. This morning it was again dead, and now it has come back to life.

As far as I can tell, the boiler is fine. When the digistat scr works (i.e. lights go on), it calls for hot water, the boiler fires and the radiators get hot. Hot water from the taps also works.

So, I think the problem is the SCR. It seems to be dying, but giving out a few last gasps of functionality.

So, is this the likely problem? If so, I noticed that the drayton digistat scr is sold alone (without the RF room control). It looks exactly like my iflo brand. Can I just buy that and have it working with my old RF room control? If so, how easy is it to install a new drayton scr over the old iflo scr?

Thanks for the help!
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I should probably add, the system has been working fine for 5 years until a few days ago.
If your any good with a soldering iron do a search for "drayton scr fix" on youtube.
I don't have an iron. The last time I used one was year 8 in school. I saw that video and it certainly looks like a simple fix if I had an iron.

But can I easily remove the old and swap one the new? Is there just a mounting bracket with wires?
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Yes it's very easy to swap these, loosen the 2 screws underneath, and lift the old one off, hook the new on on and tighten the screws. Pair the stat and receiver following the installation instructions.
Cool. So it doesn't matter that one is a Drayton and the other an igloo? They look exactly the same, but is the wiring the same?

So, I got the digistat thing and replaced and all seems to be working. Hopefully, things will continue to work.

Thanks for all the help!
I should add, for those trying the same thing, replacing the iflo scr with drayton scr is easy and requires no rewiring. The mounting plate into which the wires go in is the exact same (size, look and wiring order is the same). I used the old mounting plate and didn't rewire anything.

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