1. Bulbs:
* Check the brake light bulbs themselves: This is the most common cause. Inspect the bulbs for filament breakage. Even a seemingly minor crack can interrupt the circuit. Replace them with new bulbs of the correct wattage. Check *both* sides, even if only one side is not working. Sometimes a faulty bulb can put extra strain on the system causing other issues.
* Check the sockets: Ensure the bulb sockets are clean and making good contact with the bulbs. Corrosion can prevent a proper connection.
2. Fuses:
* Locate the fuse box: Consult your owner's manual to find the location and diagram of your fuse box (there's usually one under the hood and one inside the car).
* Identify the brake light fuse(s): The manual will show you which fuse(s) control the brake lights. Check for blown fuses – they'll usually be visibly burnt or broken. Replace any blown fuses with fuses of the *correct amperage*. Using a higher amperage fuse is dangerous and can cause a fire.
3. Brake Light Switch:
* Location: This switch is usually located near the brake pedal.
* Function: It's a small switch that closes the circuit when you press the brake pedal, activating the brake lights.
* Testing: You might need a multimeter to test the switch. With the brake pedal released, the switch should be open (infinite resistance). When you press the brake pedal, the switch should close (near zero resistance). If it doesn't close, the switch needs replacing.
4. Wiring:
* Visual Inspection: Check the wiring harness leading from the brake light switch to the tail lights for any obvious damage, fraying, or loose connections. Pay close attention to the area near the brake pedal and the tail lights themselves.
* Continuity Test: If you have a multimeter, you can test the continuity of the wires. This involves checking for a complete circuit between the brake light switch and the brake light sockets.
5. Brake Light Circuit (More Advanced):
* Tail Light Circuit: The tail lights (running lights) and brake lights share some wiring but have separate circuits that activate based on different switches. A fault in the circuit that controls the brake light specifically could exist without affecting the tail light function.
* Wiring Diagram: Obtain a wiring diagram specific to your year and model 300ZX. This will allow you to systematically trace the brake light circuit.
* Professional Help: If you're uncomfortable working with electrical systems, it's best to take your car to a qualified mechanic.
Important Safety Note: Always disconnect the negative terminal of your battery before working on any electrical components in your car. This will prevent accidental shorts and protect you from electric shock.
By systematically checking these items, you should be able to pinpoint the cause of your brake light issue. Remember to consult your owner's manual for specific details relevant to your 300ZX model.
