starting blowing the fuse for the dash lights and markers

[AndyS]

my car is a very early 1967 Euro market car, and has had wiring work done on it before. This is the first time I ever had a fuse that would blow immediately upon turning something on, in this case the lights. my actual headlights have been rewired completely with relays, so they still worked

Finally got a chance to trouble shoot it, and I found there are two banks of wires coming off the fuse (second one in on my car) One goes to all the dash lights, and the other to the markers and engine compartment and license plate lights. I separated the two output wires, turned on the lights, and checked these two wires by hooking them up individually with a fuse. the dash lights were fine. the marker lights wire blew the fuse right away. I disconnected the tail lights and front marker housings, and side markers, and the engine compartment and license plate lights. still blew the fuse, so I knew I had a bad short somewhere in the harness run to one of them, and not in the housings or their short connection wires.

I decided to just run new wires to all these components rather than try the difficult to impossible task of locating the short. Didn't take as long as I thought, and i also found a couple of iffy contacts and grounds in the process. Got everything working again. need to do another test drive this morning to confirm. You really have to keep on top of wiring issues in older cars. I have seen customers cars that have had electrical fires, and its not a pretty sight.

[RoyBatty]

Funny how this stuff works out Andy.
I just started having an issue whereby the headlights coming on blow the inline 8 amp fuse with the pink wires in my '75.
I am going to use the same process you describe.
According to the diagrams this fuse and wire circuit have nothing to do with the lights.
I have also noticed with a temporary jumper in place of the fuse, that while running the heat/def fan, when I turn on the lights the fan slows very notably. I think this is a good indication of some kind of fault in the lighting circuit, creating a large draw on the rest of the system.
Gonna go look for the leaking smoke.