RV LED Clearance Lights Turn Off When Headlights On - Grounding Fix Guide

Bottom Line Up Front

Randy, your 2002 Bounder 39Z is experiencing a classic LED conversion issue - your new LED clearance lights are going out when you turn on the headlights because of incompatible wiring between the clearance light circuit and headlight circuit. This happens because LEDs are polarized and sensitive to how power flows through the combined lighting circuits, unlike your old incandescent bulbs that worked regardless of polarity. The fix involves installing diodes to isolate the circuits or rewiring to separate the power feeds completely.

Root Causes

Your Bounder's lighting system uses a common ground setup where the clearance lights and headlights share electrical pathways. When both circuits are active simultaneously, the LEDs experience voltage drops or ground loop interference that causes them to shut off. Incandescent bulbs were forgiving of this setup because they'll illuminate regardless of polarity direction.

The specific issue is that your headlight circuit is likely feeding back through the clearance light circuit, creating a voltage drop or polarity reversal that the LEDs can't handle. This is extremely common on 2002-era Fleetwood chassis where the marker lights were designed as a single-filament system that worked with both the parking light and headlight circuits.

Additionally, your LED conversion may have changed the current draw significantly - LEDs typically draw 85-95% less current than incandescent bulbs. This lower current can cause the vehicle's lighting control module to behave unexpectedly, especially in older RVs that weren't designed for LED loads.

Before You Start

WARNING: Always disconnect both house battery and chassis battery before working on electrical systems. Use appropriate safety glasses and ensure your workspace is well-lit and dry.

You'll need a multimeter to test voltage and polarity at each clearance light socket with both the clearance switch and headlights on separately and together. Check that you have 12V positive voltage at each socket when the clearance lights should be on. Also verify your LED bulbs are the correct type - many clearance lights require single-contact bayonet bulbs (1156) rather than dual-contact (1157).

Gather these tools: wire strippers, electrical tape, heat shrink tubing, and a soldering iron if possible. You'll also need 1N4001 diodes (about $0.50 each at auto parts stores) - get at least 6-8 pieces since you'll need one per clearance light circuit. Have spare wire (18-20 gauge automotive wire works well) and wire nuts or crimp connectors ready.

Safety first - disconnect your house battery and chassis battery before working on the lighting circuits. Test your clearance lights and headlights individually before starting to confirm they work separately. Take photos of the existing wiring before making changes so you can revert if needed.

The Repair Process

WARNING: Ensure all power is disconnected before cutting any wires. Double-check with a multimeter that circuits are dead before proceeding.

Start by locating the main lighting junction box, typically behind the dashboard or in the engine compartment near the fuse panel. You'll need to install blocking diodes in the clearance light power feeds to prevent backfeed from the headlight circuit. Cut the positive wire feeding each clearance light and install a 1N4001 diode with the stripe end pointing toward the light fixture.

For each clearance light circuit, identify the wire that carries power from the clearance light switch (usually orange or brown in Fleetwood wiring). Install the diode in series with this wire, ensuring the cathode (striped end) points toward the light. This prevents current from flowing backward from the headlight circuit into your LED clearance lights.

If the diode method doesn't solve the issue completely, you may need to run dedicated power feeds for the clearance lights directly from the fuse panel. Install a new 5-amp fuse for the clearance light circuit and run new wire to each light position. This eliminates any shared pathways with the headlight system entirely.

Test your work by turning on clearance lights first (should work), then adding headlights (clearance lights should stay on). If clearance lights dim significantly with headlights on, you may have a voltage drop issue requiring heavier gauge wire or additional relay circuits. The entire job typically takes 3-4 hours for a DIY repair on your Bounder. Make sure all connections are secure and properly insulated before reconnecting the batteries and testing the complete system.

Professional Help Needed

Call a professional if you're uncomfortable working with your RV's 12V electrical system or if the diode installation doesn't resolve the issue completely. An experienced RV electrician can quickly diagnose whether you have a more complex problem with the chassis lighting control module that's common in 2002 Bounder models.

Professional diagnosis typically costs $100-150, and a complete lighting circuit modification runs $300-500 depending on how much rewiring is needed. Some shops specialize in LED conversions and have seen this exact issue many times on Fleetwood chassis - they can often complete the fix in under 2 hours with the right parts on hand.

Consider professional help if you discover additional issues like corroded ground connections, damaged junction boxes, or if multiple other electrical systems start acting up after your LED conversion. These symptoms might indicate deeper electrical problems that require diagnostic equipment and experience with Freightliner/Workhorse chassis wiring systems. A qualified RV technician will have the proper tools and experience to safely diagnose and repair complex electrical issues without risking damage to your RV's electrical system.