1999 Mazda 626 No tail lights

Do you have a voltmeter or test light and know how to use it? Do the front running lights work? When you had the head light switch out, did you see any blackened or melted spots on the switch terminals or the connector plug?

Dandy. I think this is going to be an easy diagnosis. There's a joint connector where the front and rear circuits split off. We know it's okay up to there since the front lights work. A white / red wire goes to all of the rear tail lights, and those and the license lamps all share a common ground wire. Chances are the ground wire is corroded off or got hit by something. It's bolted to the sheet metal at the center, front of the trunk. Check that wire first.

If the ground wire appears to be okay, turn on just the running lights, then use your voltmeter or test light to check for voltage on every terminal on one of the tail light bulbs. There must be at least one with 0.0 volts. If every terminal has some voltage, there's a break in the ground wire. If none of them have 12 volts, there's a break in the white / red wire.

Dandy! One in a row. Happy to hear it's solved.

That connector is listed as the "joint box", behind the left side of the dash. Three white / red wires come off of it. Two are for the two front lights. One is for all of the rear lights. If the front lights work, the circuit has to be okay up to that connector. The wire going to the rear splits into three wires, but the location of that splice is not listed.