1. Fuses: This is the easiest and cheapest place to start. Your owner's manual will show you the fuse box location (likely under the hood and/or inside the car, near the steering column). Look for fuses related to instrument panel lighting, backlighting, or interior lights. Replace any blown fuses with the correct amperage.
2. Dimmer Switch: The dimmer switch controls the brightness of the dashboard lights. It's possible the switch itself has failed completely, preventing any lights from illuminating. You may need to replace it. This is usually located on the end of the turn signal stalk (or near the headlight switch, depending on the exact model).
3. Instrument Panel Bulb(s): While unlikely that *all* bulbs failed simultaneously, it's possible. Accessing the bulbs usually involves removing the instrument cluster, a more involved process. However, if you find blown fuses, it's less likely this is the main problem.
4. Instrument Cluster Wiring/Connectors: Loose or corroded connections in the wiring harness leading to the instrument cluster are common sources of electrical problems. Carefully inspect the connectors for any signs of damage, corrosion, or loose wires. Clean and reconnect any loose or corroded connectors.
5. Instrument Cluster Itself: The most serious possibility is a faulty instrument cluster. This requires either repair or replacement, which can be expensive, and may require specialized tools and knowledge. This is less likely if fuses and dimmer are fine.
6. Grounding Issues: A poor ground connection can affect the entire electrical system, including the dashboard lights. Check the ground connections near the instrument cluster and any other relevant areas. Clean them thoroughly to ensure good contact.
Troubleshooting Steps:
1. Check the Fuses FIRST. This is the quickest and easiest step, and often the solution.
2. Test the Dimmer Switch: Try adjusting the dimmer switch to see if there's any reaction. If not, suspect the switch.
3. Visual Inspection: Carefully inspect all wiring and connectors leading to the instrument cluster.
4. Meter Check: If you have a multimeter, you can test the voltage at the instrument cluster's connector to confirm if power is even reaching the cluster. This helps isolate if the problem is before or after the cluster.
5. Consult a Wiring Diagram: A wiring diagram for your specific 1987 Cadillac Eldorado will be extremely helpful in tracing the circuits. These can often be found online through forums or repair manuals.
If you're not comfortable working with car electrical systems, take your Cadillac to a qualified mechanic or auto electrician. Improperly working with car electrics can cause further damage. Replacing a faulty instrument cluster requires specialized tools and knowledge.
