How to Pick the Correct Wire Gauge and Wire Color for your Subaru Project

In this blog post, we cover how to select the correct wire gauge for your project, as well as what the wire colors signify. 

You can purchase your automotive wire by the foot from iWire by clicking here.

When starting a wiring project for your Subaru—whether it's a full engine swap, custom lighting, or adding accessories—choosing the right wire gauge can make or break your install. Before starting a DIY project, check if iWire has already designed a Plug-and-Play Wiring Harness for your car. These include wiring kits for fuel pumps, battery relocation, extension harnesses, grounding kits, and tuning products like speed density and widebands. 

Here's a quick guide to help you choose the correct wire gauge for your next DIY Subaru build:

Why Wire Gauge Matters

Wire gauge (also called AWG - American Wire Gauge) refers to the thickness of the wire. The lower the number, the thicker the wire, and the more current (amps) it can carry. Choosing a wire that's too thin for your circuit can cause overheating, voltage drop, and even damage to your components or harness.

Common Wire Gauges and Their Uses in Subaru Builds

Here's a breakdown of commonly used wire gauges in automotive and Subaru-specific wiring applications:

• 14 AWG – A good all-around wire for mid-range power needs like relays, lighting upgrades, or gauge power feeds. Handles around 15-20 amps.

• 16 AWG – Commonly used for most accessory circuits and general-purpose wiring. Suitable for 10-15 amp circuits.

• 18 AWG – Ideal for signal wires, sensor inputs, or small draw devices like LED lights or switch inputs.

• 20-22 AWG – Used primarily for ECU connections, low-current signals, and CANbus lines. Be cautious not to use these for anything drawing real power.

DIY Tip: Plan Your Project First

Before you start stripping and crimping, outline your wiring layout. Our best tip when planning your wiring layout is to draw it out first, using different colored wires for each input. This method is one of the simplest ways to ensure your project is safe, reliable, and easy to troubleshoot in the future. If every wire is the same color, you can't tell what it's running to. Different colors matter. Here are some things to consider when planning your project:

• What are you powering?
• How much current will it draw?
• What's the length of the wire run?

Longer wire runs can experience voltage drop, so you may need to size up your gauge slightly for long-distance power distribution.

iWire's TXL Automotive Wire: Designed for Subaru DIY Projects

At iWire, we sell high-quality TXL copper wire by the foot, available in solid and striped color options to make tracing circuits easy during installs and troubleshooting. Our TXL wire is heat-resistant and flexible, featuring stranded copper for improved conductivity, and is color-coded to keep your wiring organized. It is sold in 10 ft or 20 ft strands—plenty for your project.

Color Code Cheat Sheet

Subaru OEM diagrams come with the connector, sensor, and most importantly, wire color information. Below is the notation so you can purchase the right color to match the OEM harness. 

Above are the SOLID colors abbreviations. For STRIPED wire, it is a combination of the above letters. The first letter is the base color, and the second color is the striped color.

Here are some examples:

BR - Black with Red Stripe

WL - White with Blue Stripe

PG - Pink with Green Stripe

LgBr - Light Green with Brown Stripe

SbGr - Light Blue with Gray Stripe

Wire Length Matters When it Comes to Current

The chart above is an excellent resource for determining the appropriate wire size for a 12V automotive system based on the length of the run and the amperage (current load). It is important to consider:

1. Voltage drop (ideally keep it under 5% for most 12V applications)

2. Amperage of the circuit

3. Total wire length (from power source to grounding location)

And don't forget - iWire sells prewired, color-coded pigtailed connectors that match the OEM diagrams for your year and model car for easy repair and replacement.