The JL Rubicon and many Sport S trims ship with factory auxiliary switches on the dashboard. These are fully powered and fused from the factory — you need to run a wire from the switch output to your accessory. No relay required for loads under 20A.
# Wiring Accessories to the JL Factory Aux Switches
The JL's factory auxiliary switches (labeled AUX 1 through AUX 4 on Rubicon trims, sometimes two on Sport S) are the cleanest way to power trail accessories. They're already integrated into the dash, fused through the under-hood PDC, and tied into the factory switch bank. You don't need a separate relay for most applications — lights, compressors under 20A, and similar loads wire directly.
What's already there:
Each switch outputs up to 20A (some applications derate to 15A — verify in your FSM)
The switch outputs are located at the switch control module under the dash on the passenger side
Power is present at the connector even on non-Rubicon trims — the harness runs to a connector but is capped off
Wiring diagram for your specific JL (2018–2024 varies — check your FSM or AllDataDIY)
14 AWG or 12 AWG wire (length depends on accessory location)
Weatherproof connectors or heat-shrink butt connectors
Crimping tool and wire stripper
Heat gun (for heat-shrink connectors)
Zip ties and split loom conduit
Multimeter
Panel removal tools (for underdash trim)
Locate the switch output harness
Remove the lower passenger-side underdash panel. It clips in — start from a corner and work around. No bolts on most JLs.
The switch control module is mounted to the firewall or dash structure. Look for a multi-pin connector with wires running toward the dash switches.
Identify the output wires. On most JLs, the output wires are a lighter gauge than the power supply wires. Confirm using a test light with the ignition on — the output wires should show 12V only when the corresponding dash switch is pressed.
Test outputs before wiring
With a multimeter in DC voltage mode, probe each output wire with the ignition on and the switch both ON and OFF. You're looking for 12V switched output (12V on, 0V off). Any wire showing 12V regardless of switch position is a power feed, not an output — don't connect to it.
Run the output wire to your accessory
Cut a length of 14 AWG wire long enough to reach your accessory from the switch module. Add 20% slack — it always takes more than you think.
Crimp a weatherproof connector onto the switch output terminal. Connect the other end of your wire.
Route the wire toward the accessory. Front-mounted lights typically run through the firewall grommet on the driver's side or through the existing wiring pass-through.
At the accessory end, connect power. Ground the accessory to a solid body ground near the accessory — do not daisy-chain grounds.
Seal and protect
Wrap all exposed connections in self-amalgamating tape or use heat-shrink connectors.
Secure the wire run with zip ties every 12–18 inches. Anywhere the wire could contact moving parts or heat sources, add split loom conduit.
Reinstall the underdash panel.
Fuse sizing: The factory PDC fuses the circuit, but if you add a 20A load to a 15A-fused switch, the fuse will blow. Check the actual fuse rating in your underhood PDC before assuming you have 20A.
Relay for high-draw accessories: Winches, high-draw air compressors, and roof-mounted lighting arrays draw more than 20A. In these cases, use the aux switch output to trigger a relay, and run a separate heavy-gauge feed from the battery to the relay. The switch sees minimal current; the relay handles the load.
Non-Rubicon installs: Sport S and Sahara trims may have the harness pre-run but the PDC fuse slots may be empty. You may need to populate the fuse slots — this is documented in the FSM.
Wire routing near exhaust: The passenger-side firewall is close to exhaust routing under load. Any wire crossing near that area needs conduit.
14 AWG wire (25 ft spool): $15–$25 (Ancor or similar marine-grade is best for weatherproofing)
The factory switch bank is one of the better-executed features on the JL. The work is mostly wire routing — the electrical infrastructure is already done.
Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.