help with dead CH programmer

All the common wiring setups are detailed here:

However with standard Y plan wiring, terminal 4 is live for heating on. Then you need 6 or 7 live as well (but not both) to choose DHW on or off.

Are you sure that the live feed isn't switched by an switch next to the boiler? There is usually a single switch to isolate the whole controller/boiler/pump/valve for maintenance purposes.

My thoughts exactly, no live feed to the programmer does not mean it is knackered more likely something is switched off or a fuse is blown. It has been a requirement for some time now that all controls for a CH system are powered from a single switch located near the boiler. However that does not mean that someone has stuck to that rule. At our last house the boiler was in the garage, pump , valves and wiring centre were upstairs leftover over from a previous back boiler arrangement and the programmer was in the kitchen for convenience but all were wired to the single switch next to the boiler.

Richard

Thanks John, im familiar with the wiring diagrams just that I never considered how the switching worked in the programmer so wanted a sanity check that what I was proposing would work at the wiring center end.

it was dead had power at the wiring center term 1, wiring runs under the floor cavity then up wall cavity probably eaten by mice or rats , more then one wire was OC now working ok

Wouldn't it be better to add a thermostat if the place is un-occupied?

Its most "intuitive" but with the added complexity of Y plan systems needing active signals for both hot water on and hot water off as two separate controls.

All heating systems should have an isolating switch somewhere - often an FCU. You need to check for that and make sure it is on and the fuse OK. If you can't find it, ask the previous owner (if possible)