So, I'm having the same issues as the person who posted the other thread with my '88 ST... I don't have working running lights, tail lights, or marker lights. I've checked the fuse, replaced the relay, checked/replaced many of the bulbs on the car, and my dad was checking continuity on the headlight switch earlier today. The weird thing was that we had fine continuity on connector positions 20 and 22, but not on 23 (with the switch in the proper location for each). Contact 23 is the headlight wire though, and I know that I've had working headlights on the car. I'm wondering if the light failure sensor could be faulty. I've been told on another forum that the entire circuit will shut down if there is a burnt out bulb. Is this true? Or is there a warning light on the dash? Also, where is the sensor located? My dad took out the console to clean it and found a 4 position connector under the console that didn't have anything plugged into it. Is the fuse for that circuit only supposed to have power when the switch is on? Or should it have power at all times the ignition is on like the rest of the fuses in the driver's side kick panel block? I have noticed that one of the break lights burns the dimmer of the two filaments with the brakes engaged. You can't install those bulbs backwards, so I am thinking that the wiring is backwards for the bulb. Could this be causing a fault in the tail light circuit since it is trying to light the bigger filament of the bulb? Someone mentioned that when the sensor sees lower resistance (provided by the larger wire in the brake filament) that it will cause an error. Any other ideas? I'm still not 100% sure if my headlight switch is an issue, it might be the culprit here. Maybe I have another burnt out bulb somewhere on the car. I really need to be able to get this car inspected and back on the road. If anyone does have a switch that they can sell me let me know since I'm potentially in the market for one.