The heating is working but it has started coming on and going off at the wrong time.
A problem with the time clock.
What you can do
Check the time clock. There are 2 common things that can be wrong and they are simple to reset:
- It is set to the wrong time. (This can happen if there has been a powercut (‘outage’), for example.)
- Someone has changed the time setting pins.
If this does not work
There is possibly a fault with the timer mechanism – perhaps it is starting to fail and is running slowly. Before calling a professional plumber to replace it, check it by resetting the clock to the correct time. Check it over a couple of days to see if it is slowing down.
The original timers were made by a company called Grasslin. Replacement mechanisms are easily obtainable and slide in and out of the plastic box that houses the timer. They must be compatible in size and function.
Grasslin timer guide (pdf 155Kb Right-click and ‘Save As…’ to download)