Yes, of course there's a short. I stepped into that one a bit lol. Was looking for ideas on something they might have suddenly gone bad. I know the dimmer switch thing, I'll rotate the switch and try again to see if it still instantly blows and then move on from there
It could be one of a number of things ....check the following;
* wires inside taillight fitting rubbed through or chaffed
* wires pinched under front bumper brackets or other brackets
* rusty floor pan might have damaged wires from foot traffic over the years
* poorly terminated wiring under dash touching frame or pedal brackets etc
* rust or corrosion around ceiling light rubbed through
* wiring loom going through bulkhead near battery may have chaffed through
....it could be a number of things. First thing to do is to disconnect the front-end lighting plug from the bulkhead connector, and see if fuse blows.
You will go through a few fuses until you narrow down the search....so be prepared.
Next you could try disconnecting the taillight lamps (bulbs if you like) from the fittings - a pair at a time, work methodically, and narrow down the area where the fault is.
Then do the fronts if no change and the fuse is still blowing...then rinse & repeat elsewhere there are lights or devices on that circuit.
Try the console wiring (if fitted) especially if you've had the seats out recently - or at least since the fault has been present.
Think back to when the fuse was OK, and what you did after that.
I would suggest using a series lamp for testing (saves blowing fuses) - but unless you're competent with electricity, it would be difficult to explain the process.