Switchmaster 900 replacement

[pete99mac]

I currently have a Switchmaster 900 programmer fitted to my central heating system, controlling heating and hot water.
The timer has ceased to function and I'm about to purchase a alternative replacement. My problem is that, having looked at the wiring tables given for recommended replacement controllers, they all show numbers for the terminals on the new backplate.

Do these numbers indicate the terminals to which the numbered terminal should be linked?

At present, there are only 3 wires to the 900.

I'd be very grateful for any light that someone can throw on this.

 

[75pete]

Can i ask why it has stopped working?
Did it get "turned" the wrong way when resetting the time clock?
The unit should last for the life of the boiler and is still available in stores.
Simple to remove and refit and take it back for a refund.
Do s/w off the power supply before removing it.