Busted Programmer or Something Else?

[Anatosuchus]

Hi,

I have a problem which I think might be my elderly (the sliders barely engage) Potterton EP 2002 programmer but I'd like to get a more expert opinion before I start throwing money around.

The symptoms:
If I switch on the heating alone, it doesn't come on regardless of the thermostat setting (though the "active" light on the programmer comes on so it *thinks* it should be running).
If I switch on the hot water alone it works just fine.
If I switch on the hot water *and* the heating, the heating comes on and burns continuously regardless of thermostat setting. Everyone gets very hot.

So, it's not the three-way valve because that's definitely moving. It's not the thermostat because that wouldn't be affected by the hot water setting. I guess it could be the board in the boiler but I guess that's going to be much harder/more expensive to fix.

I do intend to pop the thing off the wall when I'm feeling brave and just check the wiring is sound.

Any help much appreciated.

 

[Mike2007]

You need firstly to test for incoming voltage on the boiler terminal block. If it's live at 240vac then the problem is INSIDE your boiler.
No power, then you go to the wiring centre and test neutral - orange wire (this is live from an energised valve, 2-port or 3-port valve).
If it's dead, test the brown (for the valve, nothing else) to see if it's live going into the valve .
If it is live, either change the whole valve head of the sychronic motor side the valve head.
No power on valve brown wire? Check for incoming power from your programmer.
If that's all dead?
New programmer

 

[Anatosuchus]

Hmm, not the programmer. Don't have the tools to go poking about in the electrics too much but it might be a failed microswitch in the 3-way valve apparently. Out with the screwdrivers again.

 

[oldbuffer]

Unless you're very careful the motorised valves will have mains voltage on them. If you don't have the tools to check you might be more prudent to get someone in who has.

 

[Anatosuchus]

Yeah, definitely planning to shut down the power to that bit. I do have a mains tester and bits and pieces - I just didn't want to dive into the full-on wiring loom behind the programmer.