Thanks both. Had to wrench it off - now I can see where the screws
were but there was just no access. Must have been tiled after it was
fitted.

The backplate might be slightly damaged so I may have to replace it
anyway. Have figured the wiring out with a continuity tester.
Interestingly, the heating "Off" terminal is not wired but the water
"Off" is. What does this mean?

Thanks for the advice about a direct replacement but I really want to
move to a 7 day timer to have different times at the weekend. As for a
combined timer and thermostat - the wiring is in the wall with no easy
access and the current thermostat is upstairs. It would have been good
to move this but not easy due to the wiring not being where it's
needed.

I'm now going off to B&Q to see what I can get.

Thanks again

G.

(Lurch) wrote in message ...
On 26 Mar 2004 12:44:46 -0800, in uk.d-i-y
(The Wallport) strung together this:

Appreciate some help. The clock in this central heating timer stopped
going round and having spent hours trying to find a way to get into
the timer I broke the plastic lugs off. I'm not too bothered as I
wanted to replace it with a modern one anyway. It one with the old two
on and two off pegs around a circular clock.

Having got inside, it hasn't helped and now I'm stuck. The metal piece
at the back won't come away from the wall and it needs to to get to
the wiring which I need to do to fit a replacement. I still haven't
worked out how it was meant to come to bits but it looks like screws
from the rear and if so these are completely inaccessible. The people
who did this have cut a hole in a wall tile and so you cant get to the
very back of it. Anyone know how it is mounted?

Without looking difficult to tell if it is bodged on or mounted
correctly. It should be fitted with 2 screws on the bottom holding the
unit on to the baseplate, remove\slacken these and withdraw the front
of the unit bottom first.

When I do get to the back, what model can I replace it with? Are these
things fairly standard?

A new Horstmann H21 will fit back on as a direct replacement amongst
others.