erroneous electrical circuit

Well, its true. The third law of electrical chaos is a very real law in regard to Italian automobiles. I have two virtually identical 1977 Ferrari 308 GTB, and the wiring is not the same. One car was completed in March, and the other in May of 1977. I have found differences in the ignition feed circuit, I would have to go back and look now to tell exactly, but at any rate I now have a circuit that is not shown in any manual I presently own.

Specifically, I am refering to the fuse that feeds the left front, and right rear running lights. It blew a few days ago, shortly after I replaced some bulbs. I figured maybe the fuse was just faulty (Birdmans fuse blocks, new fuses) But instead, now it blows instantly when the lights come on. There are two plugs that are fed off the fuse, one feeds the front light, the other the rear, and on the plug that feeds the rear light, there are two wires. One wire feeds the rear light, the other goes into a cannon plug that feeds______? I unplugged the cannon plug, now all the lights work, as does everything else on the car so far as I can tell, no blown fuses. The owners manual shows nothing else on that circuit except the two lights, yet there is obviously another circuit powered off this fuse. Anyone know what that circuit might be? Later wiring diagram?

 

Just a thought, does the car have and disabled aftermarket tings usch as an old security or alarm system

 

no, I gutted all the add on BS out of the car right away. This is all factory stuff, unmolested. Its a white plug with four wires, and one of these yellow/black tracer wires runs into it. Its right under the fuse panel tucked back in behind the wires, fourth fuse from the right.

 

In my experience, yellow/black wire usually connected to a bulb of some sort, one of your light bulb socket or wire going to the socket (usually for the instrument panel or one of the guages) might have a short.

 

Some cars have a warning circuit to remind you to turn the lights off before leaving the car. To accomplish this, a connection to the parking lights energizes the (seat belt) buzzer if the lights are on and ignition is off. If you buzzer has been deactivated it may still have an errant connection which is causing the problem.

Otherwise check for homotrons. They are gay electrons which blow fuses.

 

The '78 GTB/GTS wiring diagram shows the glove box light switch (GTB only) being wired to the LF and RR taillights. It's a yellow wire (rather than yellow/black), but check out that circuit.

Regards, Kerry