Try to remember the year pulldown when starting a new thread.

OK, having working gauges and no lamp test at all makes this not a 'textbook' case of missing exciter path. The routine trouble, which might include a damaged flex fuse, takes out the gauge power too.

The flex fuse is a piece of flexible circuit on mylar used to bridge two screw terminals behind the speedometer gauge. It is usually disturbed when someone goes to pull the gauge to fix the odometer and doesn't realize the screws need not be removed.

The biggest challenges come to a new owner who finds the previous owner modified things without documenting, and the worst of them, those done to get the car sold. Typical motivations would be a check engine light, or oil pressure warning. That you have NO working lamps at lamp test yet do have working gauges eliminates the natural causes I know of, and has me suspecting the man-made troubles.

All you can do is trace the voltage. Start by fixing the alternator exciter. The alternator is probably OK because it self-excites when the residual magnetism in the rotor is enough to induce field at hi revs. This is normal. Yes, disconnecting and grounding that small red D+ wire (key on engine stalled) at the alternator should give lamp test to BAT, BRAKE FAIL, PARKING, and BULB OUT idiot lamps. The power for those lamps comes through the speedometer gauge, flex fuse, and cluster circuit traces from the ignition switch. But that power is the same needed to power the temp and fuel gauges. So you need to find out why they work, but the lamp test (warning lamps) does not.

What I would do in your shoes is pull the cluster (you've done that several times?) and go over the traces looking for signs of the previous owner, or other damage that pops out visually. Then if I saw nothing, I'd use my test lamp or multimeter to trace the voltage (cramped work on top of the steering column) to find the break. Unless someone has modified something, it has to be in the instrument panel, I think.

Here's the path of that voltage from ignition switch to the small red wire on the alt:




--
Art Benstein near Baltimore

A group of chess enthusiasts checked into a hotel and were standing in the lobby discussing their recent tournament victories. After about an hour, the manager came out of his office and asked them to disperse. "But why?" they asked, as they moved away. "Because," he said, "I can't stand chess nuts boasting in an open foyer."