Thermostat problem

[Test]

My heating has ceased working.

I have an Ideal Classic boiler which is still heating my water fine but the heating is not working even though the IMIT thermostat clicks when I turn it. The electronic controls do the timing etc. of both water and heating and it seems to still be working.

Looking at the inside of the thermostat there are 4 wires a sleeved green/yellow (earth) wire, a red (live) wire, a blue (neutral) wire and a yellow (live) switch? wire. The blue wire is not connected to anything. There are 3 terminals one of which has the red, one has the yellow and the middle one is empty.

Am I right in thinking that the blue wire could/should be connected to the middle terminal and that may be the problem? The middle terminal was hardly done up whereas the rest are tightly screwed.

Any help greatly appreciated!

Simon

[Set Square]

It's unlikely to be just that. Some stats have a neutral connection to provide a return for a little heater resistor which warms the guts up when the heating is on, and makes the stat a bit more responsive. If this resistor isn't connected, it doesn't stop the stat from working - it just makes the room temperature more likely to overshoot the setting.

When the stat is in the 'calling for heat' condition, the yellow (switched live) wire will be connected to the red (live) wire. If you install a temporary bridge between red and yellow, and this makes the heating work, there is a problem with the stat. If the bridge doesn't make the heating work, the problem is elsewhere.