I have a combi boiler which used a Honeywell rotary thermostat. I have just replaced the thermostat, as its broke, with a digital Sunvic TLX 7501. The Honeywell had 5 connections but used only 3 i.e. 1 3 and 4 and the TLX 7501 has 3 connections 1 2 3. I have got the thermostat working i.e. switching the central heating on, by connecting 1 to 3 and 3 to 2 but it does not seem to switch off when the correct temperature is reached.
Anyone got any idea as to why ?