Called a plumber who removed the electric valve to the central heating which I am sure is not the problem as it only controls whether the water goes round the heating circuit. The programmer was recently replaced so I don't think it's that. The control system generally comprises several components, a programmer, a thermostat, a motorized valve and finally the boiler and pump. The pump may be getting a live feed from the programmer. It'll run the CH for 5 minutes, then turn off for 5 minutes, repeat. The vaporstat is cutting off the boiler but it keeps cycling on. Problem: The boiler keeps running even though the thermostat is not calling for heat (the receiver in the boiler room lights up when the thermostat is calling for heat). My boiler does a similar thing. I replaced the thermostat to no avail. The boiler recently started to fire occasionally when the timer was off and the pump runs even though the timer is off. Is it normal for a boiler system to run for 3-5 minutes or so and then shut off for a minute or two and start back up again? The boiler I inspected yesterday kept turning on and off like this. Even if I turn the thermostat off, the boiler keeps running. The only thing that will fire the boiler when it is off at the programmer is the frost stat. The CH works fine, but sometimes, when it’s been on, the boiler continues to fire and the pump in the airing cupboard continues to run, after it should have gone off, ie the boiler programmer shows that the CH (and HW) is off, but the boiler and pump keep running. Hi , OK ,helps now have the model of your boiler. This issue has been going on for sometime but gradually getting worse (pump runs for longer and longer). Only resolution is to switch off at power socket. I am wondering whether it is the Honeywell aquastat controller.I have model L4080b on the boiler. To get the pump to stop going I have to turn off the boiler at the mains. Turned the heating on today for an hour, worked well, then noticed that well after the hour was up and the programmer switched off, the boiler (Ideal ICOS HE15) was still running, with a call for heat. The programmer indicates that everything is off but the boiler power light still stays on. The pressure didn’t appear to go down at all before the unit came back on… :help:I have a two zone Smith GB100W gas boiler that still runs after the thermostat has reached the desired temp. Can you tell me the model of your programmer, if you have a room stat , a hot water cylinder stat and if you have two motorised valves or one ,please. The system should be checked to determine what is powering the boiler and pump, it could be any of these components. I set the wall controls so that the heating would only come on if it was below 22 degrees (which it hasn't been yet) but noticed that the boiler is constantly making a noise. The pressure was 27 psi and the water temp was only 100 degrees. 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