Hi all, new member. I'm a decent DIYer but no electrician! We moved in to our home just less than a year ago. This evening I have replaced the thermostat on the boiler with a nest. While I was installing the heatlink in the cupboard under the stairs I noticed 2 parallel old cables. They were painted over, which was different to the other cables in the cupboard. It was located towards the top corner of the cupboard near the light and pull cable switch. To my alarm it was cut off, with bare wire exposed. I grabbed my electric testing screwdriver. Worse still. IT WAS LIVE! I flicked the switch on the consumer unit for downstairs lights (a guess because it was next to the current light) and tested again. This time my screwdriver had a dim red light compared to before. How can this be? Surely if it is on that circuit it shouldn't be live in any sense? I know you will probably tell me I need a sparky to tell me exactly what the cable is doing. And I'm aware of this. But to put my mind at rest, why would the cable still be live, but the tester says not so live?! Should I be terminating the cables some how? Thanks for your help in advance. I just can't believe someone would leave electrics in this way!