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How to tap into a car fuse box

Using a fuse tap for accessory or amp turn-on power

If you're installing a car amplifier that needs a turn-on signal or a low-power device that requires 12 volts, you can get the voltage you need by tapping into your vehicle's fuse box with a fuse tap. This handy little piece of hardware adds a new fused circuit to the factory electrical system safely and neatly. In this article, we present step-by-step instructions on how to do it.

Accele FT-ATC

What's a fuse tap do?

A fuse tap allows you to get 12 volts from your vehicle's fuse box for a low-power device, like an active signal processor, an amplifier turn-on circuit, a radar detector, or a backup camera. Because of the thin size of a fuse tap's power wire, you should only use one to power a device that will draw no more than 5 amps of current or put out no more than about 52 total watts of power.

You should not use a fuse tap to supply power for an amplifier — that would be dangerous to your vehicle's electrical wiring. An amplifier requires a thick power cable to be run from the amp directly to the battery.

How to install a fuse tap

The rest of this article will walk you through the process of installing a fuse tap. The first step is to find an appropriate circuit to tap into and make sure you have the right kind of fuse. Then install it, test it out, and button it up. Let's go.

2016 Chevy Cruze center console fuse box

Find the best fuse to tap

Step 1: Locate an interior fuse box that is easily accessible and will provide a direct and short path for the power wire to be run to the accessory.  Do not use a fuse box in the engine compartment, because the fuse tap won't provide a water- or heat-proof connection necessary for under-the-hood electrical wiring.

fuse diagram on cover located on lower dash on driver's side

Step 2: Take the cover off the fuse box. There will be a diagram or chart of the fuses with their locations and functions labeled. Identify an appropriate fuse and circuit to tap into that will power on and off with the car.

  • Good choices include the radio, an interior light, a lighter-type charger port, etc
  • Avoid using circuits for the starter, airbags, sensors, unknown "alphabet soup" labels, etc
  • You can use an empty fuse socket, if it powers on and off with the car. Test with a meter, if possible.

Step 3: Identify the type of fuse, so you can get the right size fuse tap and accessory fuse. The owner's manual should identify the type of fuse used in your vehicle

How to install the fuse tap

Step 4: Switch off the car. Remove and set aside the factory fuse.

Step 5: [Skip this step if you don't have a meter.] Turn on the car. If you have a DC volt meter, test and identify the hot (+12V) and load (0V with fuse pulled) sides of the fuse socket, and confirm that the hot voltage switches on and off with the car.

Step 6: Connect (crimp) the fuse tap wire to your new accessory device's power wire.

Step 7: With the car switched off, plug the fuse tap into the removed fuse's socket, with common side contact to the hot socket and the wire side contact to the load socket.

Step 8: Plug the appropriate fuse for the new device into the tap's accessory fuse slot.

  • The accessory fuse will be wired in parallel with the factory fuse, so the factory circuit will be fused at the sum of their ratings, which could be dangerous to the wiring if the accessory fuse is too large
  • For safety, use an accessory fuse that's rated much smaller than the factory fuse
  • Use an accessory fuse rated for 5A or less

Test, troubleshoot, then button it up

Step 9: Switch on the car and new device.

  • If there's no power or turn-on for the accessory: switch the car off, reverse the fuse tap in its socket, then turn the car back on
  • If the accessory powers on: okay

Step 10: Turn off the car, and then plug the factory fuse in the proper slot of the fuse tap, if it was removed in Step 4. (Adding a fuse to a circuit that didn't originally have one could damage factory wiring.)

Step 11: Secure the new power wire in position. Close the fuse box cover.  You may have to modify the cover to allow the fuse tap and new wire to sit neatly inside without being pinched or interfered with.

Tap into the fuse box on Jeep Wrangler in engine compartment.

Make sure you have everything

If you don't already have all the wiring hardware necessary to conveniently power-up your new device from a fuse box, give us a call or chat with us online to get everything you'll need. Crutchfield's the best place to get car audio wiring hardware like fuse taps, fuses, and hookup wire, because of the added benefits of receiving free lifetime technical support with your purchases.

  • Jamie Tolassi from Falmouth

    Posted on 1/22/2023

    Hi, I have a 2013 Ford Fiesta se that has no accessory wire and I'm trying to install an aftermarket radio. I need to tap into a fuse but am a little confused. I install the factory fuse in one slot of tap, where does the other fuse come from? Do I use the one from the back of the radio? Thanks

  • Clint moore from San Antonio

    Posted on 1/21/2023

    Saw this product in a YouTube video for hooking up Led fog lights with DRLs, does the hook up you show work the same way with the lights and is there anything special I should know about, what size fuse should be used for the fog/drl lights

    Commenter image

    Buck Pomerantz from Crutchfield

    on 1/23/2023

    Clint, This article is about adding a low-current accessory power source. Higher current devices like lighting will require a larger fuse - the value of which depends on the lighting system used and its current draw specifications.
  • Mike from Orlando

    Posted on 1/11/2023

    I have found an empty fuse socket in my fuse box to connect the add a circuit too. Is it possible to only add a fuse to the top slot as that's where the wire connects too so I can power my accessory. Am I right in thinking that there's no need to fuse the lower slot on the add a circuit as the fuse location is a spare. Thanks

    Commenter image

    Buck Pomerantz from Crutchfield

    on 1/12/2023

    Mike, A fuse tap grabs voltage from the live, powered side of the fuse socket connection, and runs it through its onboard fuse and on through the wire lead. No other fuses are required.
  • tony from Orlando

    Posted on 1/11/2023

    I have a 2WD toyota tacoma, there is a empty fuse slot labeled 4WD in the fuse box rated 15A. I want to use a fuse tap to power 30w underbody LED lighting, should I also add a 15A fuse to the tap in addition to the 3A fuse I intend to use for the LED's or should I leave the slot empty?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 1/14/2023

    Tony, A fuse tap grabs voltage from the live, powered side of the fuse socket connection, and runs it through its onboard fuse and on through the wire lead. No other fuses are required.
  • Matthew Burdett from Peacehaven

    Posted on 11/27/2022

    The fuse taps seem only to have one wire, where an appliance would usually have two. Assuming the positive wire to connect to the fuse tap, where does the return wire from the appliance go?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 11/28/2022

    Matthew, All automotive electrical devices - what you're calling appliances, I think - feature a positive connection that uses a wire connected to a fuse connected to the positive pole of the battery, and a negative connection - which, I think, you're calling a return - wired directly to the metallic body of the car (ground) which is connected to the negative pole of the battery through the car's chassis.
  • Dana from Portsmouth, VA

    Posted on 8/29/2022

    Is there a printable version of this available? VERY helpful information!

    Commenter image

    Buck Pomerantz from Crutchfield

    on 8/30/2022

    Dana, You can copy and print this article for your own use, but Crutchfield owns the copyright, so if you republish or use it for your own profit, our lawyers will reach out to you with a cease and desist order.
  • John from None

    Posted on 2/17/2022

    Do Fuse Taps have a line and load side? And have to go a specific direction? On hardwiring an item, the vehicle fuse is the bottom and the device being powered is the top. I've always been told that if you remove the top fuse, and the device being hardwired doesn't receive power, then the circuit is properly protected. Is this correct or inaccurate?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 2/18/2022

    John, The answers to all your questions are "yes." The article describes how to plug the tap in so the common side contact is in the hot slot and the wire side goes to the load socket. And if that doesn't work right, reverse the tap's position.
  • Cory from League City

    Posted on 2/6/2022

    I tapped into my headlight fuse so the light would only be on when the headlights are on, but when the car is off and headlights are off the light I tapped in is still on and won't turn off. What have I done wrong?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 2/7/2022

    Cory, I'm not sure what you're trying to do - but the electrical circuits for a car's headlights are always on, whether the car's turned off or not.
  • Ron from Beaver

    Posted on 1/5/2022

    If the vehicle has a fuse panel under the hood it will not also have one inside the vehicle.

    Commenter image

    Buck Pomerantz from Crutchfield

    on 1/7/2022

    Ron, Every vehicle I've ever encountered has more than one fuse box.
  • TG from Allentown

    Posted on 12/28/2021

    Read this article, and I have the add a circuit pigtail. Was going to use the 15 amp ACC slot. Question, the smallest size fuse I could locate was 10. This is for amp turn. Are you saying 10 is too big? Thanks

    Commenter image

    Buck Pomerantz from Crutchfield

    on 12/29/2021

    TG, A 10A fuse is way too large for an accessory turn-on circuit. In the event of a short circuit, the wire (and possibly your car) will burn before the fuse blows. Give us a call - Crutchfield carries a selection of low-current fuses that will work in your situation.
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