How to connect an additional fuse box (step by step guide)

Connecting an additional fuse box in a car is a tricky job. Most car owners hire professionals to do this, however the standard cost of wiring an automotive fuse box is quite high, so hiring a professional isn't ideal if you're currently on a minimal budget. 

Working in the electric power industry, I used to connect additional fuse boxes, and today I'm going to help you with this step-by-step guide.

Using open gaps in your car's fuse box is one of the best ways to gain access to the electrical system. Keep in mind that you will need a 12V DC source if you are installing electrical components in your vehicle.

Let's start:

Things You'll Need

• multimeter
• A pair of pliers and nippers
• Crimping tool
• Screwdriver
• flashlight
• Drill

Steps for connecting an additional fuse panel

Due to the fact that this approach partially uses the original wiring from your car, you should use it only to add connections drawing less than 10 amps of current. For high current circuits, such as audio amplifiers, you must run a separate wire from the positive battery terminal to the equipment. 

In this way, be sure to install an auxiliary fuse box near the auxiliary power supply. To avoid short circuits, always use wires and switches of the correct size and protect wiring:

Step 1: Inspect the secondary fuse panel

Finding the fuse box should be your top priority. Many modern cars are equipped with a variety of fuse boxes, which you can find either inside the dashboard or under the hood.. You can find it by referring to the user manual.

Open it, then remove each fuse individually with a fuse removal tool. Set your multimeter to 20V DC, connect the negative wire to the car body, and then check the voltage on both pins.

Step 2: Access and Label the Wires

Locate the "open" fuse slot when you open the fuse block box in your car. This is a live fuse location, but it is not connected to any of the vehicle's electronic or electrical systems. If you're not sure which slots are available, check your user manual for details on each fuse's location and function.

Remove splices, taps and unnecessary wires. You can use a marker or add tape to mark them.

Step 3: Extend the Wires

Now start extending the wires until you reach the trunk. You can use another wire to make the connection long enough to reach the back panel. Be sure to use a wire that can handle the auxiliary power to avoid short circuits.

Then cover the wires to add protection to them.

Step 4: Attach the fuse tap

Check your fuse tap to see what wire connectors it accepts. As the name suggests, the fuse tap replaces the fuse in the fuse box to gain access to the vehicle's electrical system.

Any electrical or electronic equipment that you connect will have a power cable that you plug into the socket on the fuse tap. A fuse tap often uses a straight sliding connector, but check the tap and its manual to be sure.

Using a couple of wire strippers, remove 1/2 inch of insulation from the wire that will be attached to the fuse tap. Then put the appropriate connector on the wire. Use a crimping tool to secure the connector in place.

Step 5: Connect Relay and Fuse Block

It would be better if you connected the relay switch (white) to the fuse that controls the cigarette lighter in your car to activate the relay. The relay switch will be an AMP circuit breaker and will click when your keys are in the "on" position, supplying electricity to your additional fuse block boxes.

After connecting the AMP circuit breaker relay, connect it to the fuse box. Connect the permanent fuse box directly to the positive on the battery.

Step 6: Wrap the wires and check

Install heat protection sleeves or wire protection that can withstand direct contact with very hot surfaces and are flame retardant. It would be better if you invest in wires made from a material designed primarily for use under the hood of a car that can withstand constant temperatures up to 125°C or 257°F.

Selecting the correct heat shield sleeve is essential for engine compartment wiring. Constant exposure to excessive heat can physically wear down the wiring over time, which can lead to electrical problems. The electrical resistance of a wire can also decrease due to exposure to heat, which can degrade the performance of electrical components.

Check if everything is working properly and secure the cables. 

F.A.Q.

What is the function of the car fuse box?

Your car fuse box protects every electrical circuit in your car. These electrical circuits include the main computer, engine, gearbox, and parts such as headlights and windshield wipers. (1)

Do cars have multiple fuse boxes?

Two fuse boxes are standard on most vehicles. One is used to protect engine parts such as the cooling system, anti-lock brake compressor and engine control unit. You can find it installed in the engine bay. Another is often located on the driver's side inside or under the dashboard in the cabin, protecting the internal electrical components. Numerous fuses and relays are housed in a fuse box that protects them from the elements.

Do I need to replace the fuse box in my car regularly?

Replacing the fuse box in a vehicle is neither required nor recommended unless the vehicle has suffered significant physical damage or electrical problems.

What is an auxiliary car socket?

The car auxiliary socket (also known as car cigarette lighter or auxiliary socket) was originally intended to power an electrically heated cigarette lighter. It has evolved into the de facto standard DC connector for providing electrical power to portable gadgets used in or near the vehicle directly from the vehicle's power systems. These include electric air pumps, cooling fans and power inverters. (2)

Take a look at some of our articles below.

• How to cut wire without wire cutters
• How to find a short circuit with a multimeter
• How to connect 2 amps with one power wire

Recommendations

(1) computer – https://homepage.cs.uri.edu/faculty/wolfe/book

Reading/Reading04.htm

(2) portable gadgets - https://www.digitaltrends.com/dtdeals/portable-tech-gadgets-roundup/

Video link

[How to Install Second Auxiliary Fuse Box in Your Car] | For Gauges, Lights, Camera | Episode 19