1. Fuses: This is the most common and easiest thing to check. The owner's manual will show the fuse box location and which fuses are responsible for the taillights and dash lights. Check for blown fuses and replace them with the correct amperage.
2. Bulbs: Obvious, but crucial. Check all the taillight bulbs and any bulbs illuminating the dash. They might be burnt out.
3. Wiring: This is a more complex issue. Problems could include:
* Loose or corroded connections: Check the connections at the bulbs, the fuse box, and any other relevant connectors. Corrosion is especially common in older cars. Clean any corrosion with a wire brush and electrical contact cleaner.
* Broken wires: Inspect the wiring harnesses leading to the taillights and instrument panel. Look for any visible damage, breaks, or fraying. This often occurs near flexible points where the wiring moves.
* Wiring shorts: A short circuit can blow a fuse or even cause a fire. If a fuse keeps blowing after replacement, there's likely a short somewhere in the wiring. This requires tracing the circuit.
4. Switches: Several switches could be involved:
* Tail light switch: This is often located near the steering column and is activated when the lights are turned on. It could be faulty.
* Hazard light switch: If only the taillights are out and hazard lights work, investigate the tail light switch.
5. Grounding issues: Poor grounding can prevent the lights from working correctly. Check the ground wires connected to the taillights and instrument panel for corrosion or loose connections.
6. Multi-function switch (Turn Signal Switch): This switch often controls the turn signals, high beams, wipers, and other functions. If it's faulty, it can affect the taillights as well.
7. BCM (Body Control Module): While less likely in a 1985 model, a failing BCM could interfere with electrical functions such as lights. This is more likely to cause intermittent issues than complete failure.
8. Ignition switch: A faulty ignition switch could prevent power from reaching the dash lights, though taillights are generally independent of this.
Troubleshooting Steps:
1. Start with the fuses.
2. Check all the bulbs.
3. Visually inspect the wiring for damage.
4. Check all connections for corrosion and tightness.
5. Test the switches (tail light, hazard, ignition).
6. Check the grounds.
If you're not comfortable working with car electronics, it's best to take the car to a qualified mechanic. Improper wiring can be dangerous. Remember to disconnect the battery's negative terminal before working on any electrical system.
