specZX

I see what you mean. The most recent work I had performed (4 days prior to this) was installing larger sway bars. Purely mechanical I'm afraid. I went ahead and removed the stalk assembly from the column, and removed the access cover to the "switchbox" and here's what all of the contacts look like. As far as I can see, everything looks clean and unburnt. I don't see any tears in any of the wires either. I am contemplating a venture deeper and try removing these individual contacts for further inspection, but I don't know what more there is to see.

I went ahead and followed your additional advice and here's what I found: I went ahead and physically pulled the plugs on each light circuit including the Headlights, Side Markers, Front turn indicators, rear taillight assembly, and the license plate light. Surprisingly and unfortunately, no change in result. The fuse still immediately blows with voltage drop when I turn the parking lights or headlights on despite everything being unplugged. Next, I ran some tests at the plug for the combination switch via the positive of my multimeter connected to the fuse terminal and the negative for probing each terminal in the plug for the combination switch. I took a voltage reading, and resistance. Red with White Stripe: Voltage, No resistance Red with Green Stripe: Voltage, No Resistance Red with Yellow Stripe: No Voltage, No resistance Red with Blue Stripe: Voltage, No Resistance Red Solid: Voltage, No Resistance Red Solid #2: No Voltage, 0.6 ohms of Resistance Yellow with Black Stripe: No Voltage, 21.2 Ohms of Resistance Green with Blue stripe: Voltage, No Resistance Green with Red Stripe: Voltage, No Resistance Green Solid: Voltage, No Resistance So, the only wires in the plug that showed resistance was one of the Solid Red wires, and the Yellow with Black Stripe. However, I think these two go to the Fuselink, at least that's what the FSM leads me to believe. So I assume I should ignore that. Unfortunately, it seems I am chasing a ghost now. Is there perhaps another plug in the harness somewhere for this circuit that could be melted, or is it possible that the fuse box could be failing just on that terminal?

I assume that could be any of the positive wires that go to any of the bulbs. If this is the case, is there a typical area of the harness in these cars that is known to be a wear spot?

First things first, my car is a Base, completely non optioned '79 5-speed 2 seater built in 10/78. All of my electrical components aside from the stereo are original/stock and unmodified. The issue that I just started having is my 15A glass fuses for the "Clear Tail" circuit of the fuse box blows IMMEDIATELY and VIOLENTLY (Voltage dips to about 10V, big spark, sometimes with an audible pop) upon turning the headlight switch to either "Park" or "ON". When this happens, I lose every single light on the vehicle aside from the high beams, Brake lights and the interior dome lights. According to the FSM, this circuit sends power to "Light warning lamp, Illumination lamp, license plate lamp, side marker lamp, clearance lamp, tail lamp" The first thing I did to kick off diagnosis was pull the column covers off, and inspect the connectors that go to the light switch/stalk. To my surprise, they all looked to be in excellent shape with absolutely no signs of melting or corrosion. Next, I started the process of elimination. I unplugged every light on the parking light circuit including: Tail lights, side markers, front turn signals, and the dash dimmer switch. I removed each bulb. I did not unplug the license plate lights because they didn't work to begin with. The rear tail light sockets had some slight corrosion (thin layer of white powder substance) but other than that, the sockets looked to be in perfect shape. Once I did this, I popped a new fuse in, turned the switch, and results were exactly the same. The voltage meter dipped followed by a Big spark, and a pop of the fuse. Out of all the Six Z's and ZX's I've owned, I've never had any issue up until this point with Fuses popping so suddenly and consistently. I am looking for advice on how to continue with my diagnosis. Is there a possibility that a relay is causing the short? Could the Fuse box itself be going bad? (No other fuse terminals have this issue) Or have I missed something obvious?