[Ivy66GT]

Turns out my fog light circuit breaker is broken. Not a big problem as I see new ones are $10. But while testing to discover this I found that my wiring doesn't exactly match what I expected. The only schematic I have for the fog lights is one from Veronica's blogsite. So this is a question about her schematic: Fog+light+wiring.jpg (image)

Mine is a July '66 San Jose factory GT with the fog light harness, C5ZB15223C, hooked into the tail lights. The power to the fog switch from the circuit breaker comes through a blue-black wire which agrees with the above schematic. However, the schematic says power to the breaker is from the ignition switch through a black-yellow wire. On my car both wires on the breaker are similar blue-black wires both of which have molded on ring connectors so they are almost surely original. I don't know where the blue-black wire providing power to the breaker comes from since it disappears into the harness. But wherever it is, there is 12V on the breaker any time the battery is connected; it is not a switched power source.

Is the above schematic for 1965? Was there a change in how the 1966 fog lights received their 12 volts? Once I get a new breaker I won't need a key or anything for fog lights - just flip the FOG switch.

[66Sprint200]

The wire that gives power to the breaker goes into the yellow wire in the main underdash harness that supplies power to the headlamps. I am not doing it that way when I put the fog lamps in because apparently it can weaken/ wear down the headlamp feed over time. I am going to attach it to the post on the back of the ignition switch to supply my fog lights with power.

[Ivy66GT]

The blue-black splices into a yellow wire somewhere upstream? There is no obviously yellow wire associated with any of my fog wiring.

[66Sprint200]

I know, it seams odd. In you main underdash harness there is a yellow, or yellow-black wire that gives the headlamps constant power so you can turn them on without a key. For the cars that got foglamps, the factory spliced the black-blue wire into it then wrapped the harness to hide the joint because it is just a little splice. They had already put the feed into my repro harness, but I had to cut it out after my brother mistakenly hooked it to the dash thinking it was a ground. Luckily no other wiring was damaged, just the foglamp feed.

[Ivy66GT]

OK, thanks for the explanation. With the harness in the car that would be kinda difficult to discover.

The blue-black feed wire seems to sprout out of the main harness at the same point as the two green wires going to the brake light switch. On a spare harness I have there are only the two green wires and no blue-black wire there. But that is a non-instrument and also a non-hazard flasher harness which I think means its from a '65.

I am still curious as to what cars used the black-yellow feed wire as in the referenced schematic and where on the ignition switch did it connect?

[66Sprint200]

If you decide to connect it to the ignition switch which is essentially the same thing as splicing into the headlamps, you will connect it to that threaded stud on the back. This means you will have to stick a loop connector onto the black-blue feed wire.

[Ivy66GT]

For those of you wanting to know what's inside the circuit breaker see the attached photos: one from the side, the other from the top of the breaker widget. A heavy steel strap spot welded to the steel terminal makes contact with the other, copper terminal.

Carefully pry back the 4 crimps, ease out the Bakelite base and the parts inside are so sturdy they is little to go wrong. Except, that is, oxide forming between the contacts over the last 43 years. Gently pry the contacts apart, scrape their surfaces, reassemble - it should be good for another 40 years. There was nothing to seal the case originally so not sealing it seems only reasonable.

The connection posts are marked for polarity but knowing what's in there I doubt it makes a lot of difference which way you hook it up.

[Ivy66GT]

Since you can't easily get down between the contacts I had to use citric acid to clean the contacts before getting reliable operation. But then I tend to put citric acid on and in a lot of things.