# Eight fuses, and one socket is already empty > A fuse box diagram lists eight circuits by what breaks if they fail, printed on the lid that only gets opened once something already has. August 19, 2026 · https://justog.club/stories/fuse-box-diagram Eight numbered positions in a grid, each with an amp rating and a circuit name: 10A SIDELIGHTS, 15A WIPERS, 20A HEATER, 10A INSTRUMENTS, 30A HEATED REAR, 15A HORN, 10A INTERIOR, 20A FUEL PUMP. Position five is empty. No fuse sits in the socket, and it's ringed in red. ## What is this, exactly? The key to every circuit in the car, printed where the fuses actually live. It's moulded or printed straight onto the lid that covers the fuse box, not filed away in a handbook somewhere. Open the lid and the answer to "which one is it" is right there, on the same piece of plastic as the fuses themselves. ## Why put the chart on the lid instead of in the manual? Because the two moments when this information is useful — right now, in bad light, with something already not working — are exactly the moments nobody wants to go looking for a book. A chart on the lid is readable at the worst possible time and invisible the rest of it. Nobody studies a fuse box diagram for pleasure. It sits there doing nothing until the heated rear screen stops clearing, and then it's the document in the car that actually matters. The wiring behind that lid carries a version of the same idea one layer further in — [colour standing in for a chart, with no chart needed at all](/stories/wiring-loom-colour-code). ## What does the empty socket actually tell you? That somebody has already been here. A missing fuse in position five means a decision, not a fault: somebody pulled it, probably to free up a socket for something the car didn't originally carry, or because that circuit stopped mattering to them. The chart still lists HEATED REAR at 30A whether the fuse is fitted or not — it's describing the design of the car, and the empty socket is a separate layer, a record of what one owner actually did with it. Read together, the two things are more honest than either alone: the chart says what the car was built to do, the gap says what somebody decided it didn't need to keep doing. ## Can a real manufacturer's fuse layout go on a shirt? The amp ratings and circuit names are facts about how a car's electrics are organised, and [a wiring diagram's correctness is what makes it worth reading](/stories/electrician-trade-shirt) — none of that belongs to anybody. A specific manufacturer's actual box layout, part numbers or badge are different — drawn artwork and marks that belong to the company that made them, licensable the usual way if a real one's the point. Eight generic circuits, invented positions, is the same information doing the same job without asking. ## Does it work for a vehicle other than a car? Anything with a fuse box has one of these, and most of them are shorter and stranger than a family car's. A motorbike's box might carry a handful of circuits. A narrowboat's might mix low-voltage lighting with a bilge pump on the same board. The specificity is what makes it worth wearing rather than the number of circuits — a chart with a genuinely odd mix of the things it protects is more particular than a tidy generic one. ## Isn't a list of what breaks a strange thing to want on a shirt? Only if you think of it as a list of failures rather than a map of the whole electrical system, described by its weak points. Eight lines cover sidelights, wipers, heater, instruments, the heated screen, the horn, the interior light and the fuel pump — most of what a car actually does that isn't propulsion. A chart that tells you exactly what stops working, and by how much current, is a more complete picture of the car than a diagram of what's supposed to go right. ## Does it print well? Yes — a numbered grid with short labels is close to ideal artwork, and the empty socket gives it a single strong focal point for free. Keep the amp figures and circuit names larger than the real lid would set them; small numerals are exactly [what a weave loses first](/stories/bold-shapes-survive-fabric). Sand or oil-black work well as a ground. Black for the grid, red for the empty socket and its ring, is enough — two inks, one of them doing all the drama. ## How do I get one made? Describe the box at [JustOG](/) — how many circuits, which ratings, and whether a socket should sit empty. Pick a direction, drag the crop frame, see it composited on the real garment, and it's made to order and shipped. Designs other people have published are in the [shop](/shop). Seven fuses doing their job, and one ring of red where the eighth used to be.