Not that I want to light cigarettes or anything, but I'd like to know that my tyre compressor or phone charger will run if I need them to. Have checked the fuse and it seems OK, but I'm getting nothing from the compressor (which works in our other car) and the lighter itself, when I dug it out, didn't work either. Any ideas? Car doesn't seem to have been a smoker's car before I got it last month.

Got a test light?

Phase tester? Now why didn't I think of that?

12v test light will do, Halfords and motorist centres usually sell em. Well worth having in your kit.

Got electric windows? Make sure that the isolator switch for the rear is not on, this will also cut the power to the cigarette lighter.

Y'know - I have electric windows and the isolator switch IS switched on, to stop the kids winding them up and down incessantly. I bet that's what it is - I'll check that first thing in the morning.

Given the location of the cigarette lighter, that's an extremely clever interlock to include.

Thanks all for your help so far.

fordfan - you got it in one. Perfect - at least I know now. I suppose the only problem with that as an interlock is that you can't run a car charger for a phone or anything else, while you've got meddling kids in the back. Just have to condition them to expect that the switch will be on and then I can do what I want.