Adding a Circuit – Fuse Tap Install in a Jeep TJ

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Fuse Tap Install in a Jeep TJ

Whether you’re wiring up a phone charger, CB radio, or powering a relay for off-road lights, tapping into your TJ’s fuse box with an add-a-circuit fuse tap is one of the cleanest and most efficient ways to get switched power without butchering the factory harness.

What Is an Add-a-Circuit Fuse Tap?

An add-a-circuit (also called a fuse tap or fuse piggyback) is a compact adapter that plugs into an existing fuse slot and splits it into two protected circuits—one for the original fuse and one for your accessory. It’s available in different sizes, and for the Jeep TJ you’ll typically want the ATO/ATC size for the interior fuse panel under the dash.

Why Use One?

Running new power wires in a TJ can be a hassle, especially when you’re trying to avoid cutting into factory wiring. The fuse tap solves this problem neatly. It draws power from a factory fuse location, giving you a new fused circuit without any permanent modifications. It’s ideal for:

• Dash cams
• Aftermarket radios like a CB or GMRS
• USB chargers
• Auxiliary switches or relays
• LED lighting systems

Best of all, it’s reversible—pull it out and the Jeep’s fuse box looks untouched.

When not use One

A tap is convenient and easy but isn’t really a good choice for something that requires a higher power demand like an on board air compressor. In this case finding a good and proper connection within the existing wiring is probably a smarter move. Often high demand systems will use direct/fused battery power that’s controlled through relay.

Installing the Fuse Tap

Tools & Parts Needed:

• Add-a-circuit fuse tap (ATO/ATC type)
• Two fuses (one for the original circuit, one for the accessory)
• Crimp connectors or solder and heat shrink
• Wire stripper/crimper
• Multimeter (optional but helpful)

Installation Steps:

1. Identify a Fuse Slot:
   Choose a circuit that’s only on with the ignition. In the TJ, the radio or cigar lighter fuse slot is a common choice.
2. Pull the Fuse:
   Remove the original fuse from the chosen slot and install it into the lower slot of the fuse tap (this maintains protection for the original circuit).
3. Insert a Fuse for the New Circuit:
   Place an appropriately sized fuse in the top slot—this protects your new accessory.
4. Crimp Your Power Wire:
   Use the pre-attached wire lead on the fuse tap to crimp or solder your 12V accessory power wire. Make sure your connection is solid.
5. Plug It In:
   Push the fuse tap into the original fuse slot, routing the new wire neatly out of the way. Avoid sharp edges or moving pedals.
6. Ground the Accessory:
   Don’t forget—your accessory still needs a good ground. Use a body bolt or chassis ground point nearby.
7. Test It:
   Turn the ignition key and verify power to the accessory. Check that both circuits work and fuses are seated correctly.

The TJ has a small circuit block behind the glove box that is easily accessible and many TJ’s have an unused circuit or two that won’t interfere with anything when using the tap. We used the circuit that was originally for the rear wiper, since the jeepfan.com 2004 TJ doesn’t have a rear wiper that circuit is unused and a perfect candidate.

We used the circuit tap for power to the air locker control switches as well as a CB radio.

Benefits for the Jeep TJ Owner

• Clean, Professional Install: No T-taps, no wire splicing—just a neat plug-and-play upgrade.
• Switched Power Made Easy: Great for devices that shouldn’t drain the battery when the Jeep’s off.
• Easy to Remove or Reconfigure: Want to change the accessory or move to a different fuse slot? No problem.
• Ideal for Relay Triggers: When setting up rock lights, underhood LEDs, or aftermarket fogs, the fuse tap makes for a perfect ignition-triggered relay feed.

Final Thoughts

Adding circuits to a TJ Wrangler doesn’t have to mean tangled wires and guessing games. The add-a-circuit fuse tap brings structure and simplicity to your wiring projects. Whether you’re building out a trail rig or just need a clean power source for your GPS, it’s one of the handiest low-cost upgrades you can make.

If you’re wiring up multiple accessories, you might even consider a dedicated fuse panel down the line—but for single circuits, this little adapter is hard to beat.

jeepfan.com 2004 Jeep Wrangler TJ Unlimited