* Wiring Issues: This is the most common culprit. Look for:
* Broken wires: Check the wiring harness running from the turn signal switch to the lights, both under the dash and behind the panels. Look for any cuts, chafing, or corrosion, especially near areas that flex frequently.
* Loose connections: Inspect all connectors and plugs along the wiring harness. Corrosion or loose connections can interrupt the signal.
* Ground Issues: A poor ground connection can prevent the lights from working. Check the ground points for the tail lights and turn signals. These are usually metal points on the vehicle body near the lights. Clean them thoroughly.
* Wiring shorts: A short circuit can blow a fuse, but sometimes a partial short might not be enough to blow it but enough to disrupt the signal.
* Turn Signal Switch: The switch itself could be faulty. It's a common wear point, especially if the switch is used frequently. Testing the switch with a multimeter will be necessary to confirm this.
* Multi-Function Switch (Combination Switch): This switch often controls turn signals, wipers, and other functions. A problem here could affect multiple systems.
* Brake Light Switch: Located near the brake pedal, this switch might be failing to send the correct signal when the brake pedal is pressed. It's a relatively inexpensive and easy part to replace.
* Bulbs and Sockets: Although less likely if *all* brake and turn signals are out, check the bulbs themselves. A burned-out bulb in a cluster can sometimes affect others in that circuit (though less likely with separate brake and turn bulbs). Also examine the bulb sockets for corrosion or damage.
* Trailer Wiring (if applicable): If you've recently used a trailer, a short in the trailer wiring harness can sometimes affect the van's lights.
Troubleshooting Steps:
1. Visual Inspection: Start with a thorough visual inspection of all wiring and bulbs.
2. Check Bulbs and Sockets: Replace bulbs (if applicable) and inspect sockets for corrosion.
3. Test the Brake Light Switch: A simple test with a multimeter can verify if the switch is functioning.
4. Test the Turn Signal Switch: More involved testing with a multimeter may be needed here.
5. Trace the Wiring: Use a multimeter to trace the wiring from the switch to the lights. Check for continuity and voltage at each point.
6. Ground Connections: Clean and tighten all ground connections.
If you're not comfortable working with electrical systems, it's best to take your van to a qualified mechanic. They have the tools and expertise to diagnose and repair the problem efficiently. Be sure to explain the issue thoroughly, mentioning that fuses and relays have been checked.
