I’ve written this in the hopes that it is easy enough for some one with no experience to understand and to give them the confidence to try to find faults or diagnose where a problem lies. If it isn’t as clear as I’d hoped then post up, ask questions, pm me (or Im sure Matty would be happy to answer questions or others in the buisness) This might get a bit long (like my usual posts! :) so I’ll try to break it up over a few posts to make it a bit easier to read. I’ll also be adding some pics at a later date to the original posts. My background (if your interested) I served a 4yr apprenticeship in electrical and electronic engineering, I’ve got C&G’s in electrical installation, ONC, HNC and currently completing my HND in electrical/electronic engineering, various other electrical qualifications, I’ve got 20 years experience in electrical systems, Im a senior design engineer and I’ve been a design engineer for 6yrs…..enough of the big headed stuff : :-[ Before going any further it is useful to understand some terminology which I might be using Circuit – When I refer to a circuit I am referring to a whole system - the supply +Ve through switches, lights etc and back to –Ve Components – the individual bits of a circuit but not including the wires ie switches, bulbs(lamps), heater elements, motors etc Parallel – connecting in parallel means connecting something across another component, if you put the leads of your tester across battery terminals, either side of lights or across a fuse (without disconnecting or removing those components) then this is connecting in parallel Series – connecting in series means connecting something in line with. So if you disconnect your battery +Ve lead, connect one of your tester leads to the battery post/terminal and the other tester lead to the disconnected +Ve lead of your battery then this is connecting in series. Any current will have to flow through your tester.