67 Mustang Instrument Lights Not Working

Hello! New to the forum and new to vintage car ownership. I’m somewhat handy, but I’ve realized I’m out of my depth. Electrical definitely isn’t my thing. I can’t get my instrument lights to work, but everything else seems to be working. The headlights, the tail lights, the reverse lights, the instrument panel brake light, h/l light, turn signals, (when I press the brake the emergency flashers go solid) but otherwise, they blink, the radio has power and lights, the shifter has lights, the fog lights work. I replaced the light switch because it was suggested all over the place that’s probably the culprit due to corrosion, but seems it wasn’t the problem. I’ve attached two photos in the hopes one of these two items may be the culprit. I’m not sure though. Any ideas? I have no idea why there’s a wire with connector plug to the light switch that’s unused. I also see what could be a short on the IVR, I’m not sure why it was spliced like this, it appears to go to one of my gauges. Help!

That unused plug from the headlight switch connector is for the optional fog lamps that were on the GT option.

Likely the instrument lamps do not work because the fuse panel is corroded. The shortest fuse is for the instrument lamps. Typically you have to polish the contacts with a Dremel and a small brush to get contact.

Royce thanks so much. I wondered about that, I’ve seen some other posts regarding fuses, but I wasn’t too concerned since the fuse appears to be in tact and everything else works. Would that fuse just control the instrument panel lights? For example, I had ruled it out since the turn signals, brakes, and H/L indicators work, and the wipers (not sure if they’re on there too). But if you think it’s still possible it’s the fuse, I’ll have to get in there and polish those contacts up.

Measure across the fuse with a volt meter. Every one I have checked has been bad.

What kind of reading should I be getting? And should I measure with the fuse in or out? Thanks. I was thinking if my radio works maybe the 2.5 isn’t bad, but who knows how they hooked up my radio and to where. So that’s not for sure going to rule out that fuse.

Just set the volt meter to read 12 volts. Leave the fuse in place. Measure on both sides of the fuse and the fuse holder.

Voltage to the dash panel fuse is controlled by the headlight switch rotation position. So long as both sides of the in-place fuse shows the same voltage (non-zero), you can rule out the fuse itself. Measure on the clips, not the fuse, as the outgoing side of the fuse may not be making good contact with the clip.

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