* Fuse: Check the fuse box(es) for blown fuses related to the taillights and dashboard illumination. Your owner's manual will show you the fuse layout and what each fuse controls. There might be separate fuses for the left and right taillights, and another for the dashboard lights.
* Wiring: A broken or corroded wire in the wiring harness is a common culprit. This is especially likely in older vehicles like a 1999 Jeep Wrangler, where wiring can be exposed to the elements. Inspect the wiring harness leading to the taillights and the dashboard for any damage, fraying, or corrosion. Pay close attention to the connections at the lights themselves and the fuse box.
* Tail Light Assemblies: While less likely if the problem is across both sides, it's possible a problem within the taillight assembly itself (bulb socket, ground wire) is preventing the taillights from working. Inspect the bulbs and sockets in both taillights.
* Dash Lighting Switch/Circuit: The issue could be specific to the dash lighting. The dimmer switch or a related circuit could be faulty.
* Ground Connection: A poor ground connection can affect multiple lights. Check the ground wires for both the taillights and the dashboard. These are typically black wires connected to bare metal on the vehicle's body. Corrosion on these connections is a frequent problem.
* Multi-Function Switch (likely less probable, but possible): This switch controls various functions, including turn signals, wipers, and sometimes lighting. A problem here *could* affect multiple circuits, but it's less likely to isolate to just taillights and dash lights while leaving brake lights working.
Troubleshooting Steps:
1. Start with the fuses: This is the easiest and quickest check.
2. Visually inspect the wiring: Look for any obvious damage.
3. Check the bulbs and sockets in the taillights: Make sure the bulbs are good and the sockets are clean and making good contact.
4. Test the ground connections: Clean any corrosion you find.
5. If you have a multimeter: This allows you to test the voltage at the lights and fuses to pinpoint the problem more accurately. Measure voltage at the fuse, at the wire leading to the taillight, and at the light itself. Low or no voltage indicates a break in the circuit.
If you're not comfortable working with car electrical systems, take your Jeep to a qualified mechanic. Incorrectly diagnosing and fixing electrical problems can lead to further damage.
