Help identifying a couple of wires

[peeeot]

I have 2 1960 Thunderbirds to examine (one coupe, one convertible), and both of them differ from every wiring diagram I can find on a couple of key points. If anyone can ID the following wires for me, I'd appreciate it.

1. There is a bluish-green wire paired with the yellow wire on the Bat terminal of the ignition switch. This wire has a black plastic fuse holder on it just a few inches away from the terminal. On both cars, this black fuse holder is different than any of the others in design, and houses a 14A SFE fuse, though the wire appears to be just 18 gauge or so. None of the diagrams show this wire or fuse holder nor reference the fuse. What is it?

2. There is a blue wire with a black terminal end installed on what I believe to be the "A" terminal of the headlight switch. Both cars have it in the same place, but again, no reference to it in the diagrams. The diagrams and the article on this web site reference a green wire in this position, but neither car has this green wire. What is the blue/black wire for?

I will note that the convertible's headlight switch does not have the dome light terminals on its underside like the coupe does. I don't know for sure whether the switch is original but it is marked FoMoCo.

[jopizz]

The green wire with the fuse is for the stop light switch. The wiring diagram in the TRL clearly shows it.

https://www.squarebirds.org/Diagrams-Schematics/1958-1968_Wiring_Diagrams/60TbirdWiringDiagram.jpg

I'm pretty sure the blue-black wire is for the glove box light. It was optional so it may not be on all wiring diagrams. The diagram in the TRL shows the wire but not the color.

John

[peeeot]

Beautiful, thank you! I was working off of the un-edited version of that diagram as well as the diagrams in the factory service manual. I didn’t realize ya’ll had corrected the diagram on this site—thanks for clueing me in.

Do you know what the fuse rating for the stop light circuit should be? 14A seems excessive.

[jopizz]

The parts book shows 7.5 amp for the stop lamp circuit.

John

[peeeot]

John, could you share the reference you used for the 7.5A stop light fuse value?
Do you happen to know the trip values of the internal circuit breakers in the headlight switch?

I thought it odd that both of my birds had 14A fuses installed in the stop light circuit. In 1959 the stop lights were powered via the internal circuit breaker to the A terminal of the headlight switch, which I suspect was 12-15A based on web references to later Ford headlight switches. However, 4 1034 bulbs should draw 7.2A (1.8A each) on their bright filament and the wire gauge is only 18 so a 7.5A fuse makes some sense.

[jopizz]

Here's the chart from the 1960-64 Master Parts Catalog. I don't know the internal value of the headlight switch. I'll look around some more. The only 14 amp fuse listed for a Squarebird is for the blower motor. 1958 and 1959 Thunderbirds had a stop light relay in the trunk. In 1960 they did away with that and used a fuse instead.

John

glass fuse chart.jpg dome lamp fuse.jpg

[peeeot]

Thanks again! I did not think to look for fuses under "breaker assembly." Presumably you and/or others have been using the SFE 7.5 fuse without any issues in the stop light circuit so I will do the same.

One other wiring clarification: I believe the diagram is incorrect regarding the backup light circuit. It shows the power supply coming from the A terminal of the headlight switch, but that is an always-hot circuit. On my coupe it looks like the black wire from the R terminal of the headlight switch goes to a 4-way connector; another black wire proceeds from here to the taillights while a black/red wire goes from the same connector to the back up light switch. So, the back up light switch is powered by the R terminal and only works when the parking lights or headlights are on. Does that sound correct?

[jopizz]

The backup light goes through the neutral safety switch unless you have a manual transmission. Then it has a separate switch on the transmission linkage. I've found that the backup lights only work when the lights are on which is what you have also. It makes more sense however to have it like the wiring diagram so they work all the time.

John

[peeeot]

The blue-black wire on the A terminal of the headlight switch goes to the clock fuse holder. I just verified it after isolating the wire at both ends.

[jopizz]

Odd that all the wiring diagrams show it branching off from the lighter and going to the B terminal.

John

[peeeot]

The plot thickens...a little. I obtained some SFE 7.5 fuses and went to install one in the stop light cartridge. The fuse is not long enough to load the spring in the cartridge more than the tiniest bit; it really seems like the cartridge wants a longer fuse to make good secure contact with the terminals.

While digging further into this I came across this thread:

https://www.squarebirds.org/vbulletin/forum/-1958-to-1960-thunderbirds-general-technical-discussion/-1958-to-1960-squarebirds-general-technical-discussion/1028-no-brake-lights-all-others-work/page2?t=952&highlight=stop+lights

where, in post #22, Alexander states that "The assembly manual for 1960 shows the brake switch wire (#18 geen wire) going to a 14 amp fuse in line with the Battery terminal of the ignition switch." He reaffirms this in post #26.
Additionally, LuckyJay confirms the SFE 14 fuse in post #28.

So, I'm sticking with SFE 14 for the stop lights.

One other note on fuses: almost everything references a 1AG-5 fuse for the turn signals (except one of the shop manual diagrams on page 12-18, which shows a 7.5 for the signals). A 1AG is a very short 5/8" fuse and is too short for the holder on the 1960 headlight switch, which is set up for a 7/8" long fuse like the SFE-7.5. Apparently in 1959 the lower (turn signal) fuse holder was shorter and sized right for the 1AG-5, but in 1960 they changed it. My solution for this is to use an AGW-5, which is the same dimensions as the SFE-7.5.

[jopizz]

Considering the wire only goes from the ignition switch to the brake switch I guess 18 gauge wire with a 14 amp fuse is ok. It still seems kind of thin for that size fuse though.

John

[simplyconnected]

Take this to the bank...Fuses are there to protect your wiring, even in your house. They are not there for personal protection or to protect the end device. (Our National Electrical Code is written and enforced by the National Fire Protection Agency.)

SFE fuses have lengths that correspond to their amperage. This was a way to make sure a larger capacity fuse was not used in the circuit.


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Other glass fuses, like AGC and many more, are all the same length regardless of amperage up to 30-amps. - Dave