Subaru Legacy Fuse Replacement

Date: Jan 21 2023

Experience: 10 amp fuse replacement on a 2015 Subaru Legacy

Outcome: Success

Learning: The importance of the user manual; basic automotive electrical system maintenance; confidence in simple troubleshooting.

Notes:

This experience started in the early hours of a Saturday morning. Before sunrise, I was driving on the highway to the archery club. Several other drivers rapidly flashed their headlights while they approached from behind. After the third person flashed me I understood the message: “Lights!”

The problem had not been immediately obvious because the signal lights had been working. After I pulled over, I confirmed that the running lights in the tail were out. I should have anticipated this problem because I used a second-hand wiring harness to connect a U-Haul trailer the week before. Obviously, I had overloaded the circuit.

To date, I had never changed a fuse in the car. That Stubborn Amateur feeling came upon me. That intuition about a problem that is laughably simple for an expert. The only thing stopping me from solving this problem was some basic knowledge and experience. In fact, the longer this notebook entry becomes, the more ridiculous I feel writing about the simplicity of changing an automotive fuse!

Getting flashed by other drivers on the highway.

Discovered the tail lights were not working.

Both lights were out so it was a problem with the whole circuit and not just one light bulb.

Recently used questionable wiring to power more lights for a trailer.

The fuse is probably blown!

Lets be honest, the internet enables a Stubborn Amateur. A quick look at the internet of course directed to the user manual. This was a straight forward problem - the tail lights were out so the 'Tail" circuit must be the problem. The Tail circuit is listed as fuse panel 4 in the diagram above.

If other electrical equipment had failed additional research would be needed to identify the circuit abbreviation. Overall, the circuit naming conventions in the manual seemed intuitive. Thanks Subaru!

I learned that there are 2 fuse boxes: one under the hood and one under the steering wheel. The manual indicated that the Tail fuse is under the hood. Expect for 8 years of dust, the picture of the fuse box in the manual looked just like real life. Again, thanks goes to Subaru for also including a diagram under the fuse box cover. Troubleshooting this problem was really easy. The Tail fuse was immediately identifiable as fourth from the left and marked by a '4' in the diagram.

I did not have the plastic fuse puller tool. I attempted to pull the fuse with my fingers but couldn't get it. I did have a pair of hemostats in the trunk that made the work easy.

The Stubborn Amateur definition of a fuse:

A fuse contains a thin piece of conductive material that is designed to burn up if too much electrical current passes through. We want to protect the other components in an electrical circuit from too much current. It is better for the fuse to burn up than another component. Burning components might cause a fire and are certainly more expensive to replace than a little piece of fuse. We can see the fuse pictured above on the left is clearly broken. The thin conductive material inside the fuse on the right is intact and ready for use in a circuit.

Current is measured in Amps.

A fuse's current tolerance (in amps) is printed clearly on the fuse itself. Pictured above is a broken, red, 10 amp fuse.

I learned this time that there are different automotive fuses. The best advice when replacing a fuse is to take the broken fuse to the automotive store and find a replacement that matches. The 2015 Subaru legacy uses what are called "low profile, mini fuses." Five 10 amp low profile mini fuses cost $7.50. I now have extras for future blown circuits.

If the amp value of a fuse is too low for a circuit it will burn out and need to be replaced again. If the amp value of the fuse is too high it wont burn out when it needs to which might lead to damage or a fire. Use the same type of fuse when replacing them! The Tail circuit had a 10 amp fuse so I replaced it with a 10 amp fuse.

It is difficult to see in the daylight but the tail lights are now operating.

Thanks to the other drivers for flashing their lights at me in the morning. It was a friendly way to let me know the car had a problem. I wrote this article to document the first time I changed a fuse. It was VERY easy. I have spent much more time writing than the job itself. It was good exercise for me to document the process.

The most difficult aspect to this problem was confronting the anxiety of not having done it before. This story is appropriate for the Stubborn Amateur as an example for others to overcome any inhibition when solving new problems. Common sense, creativity and the stubborn pursuit of a solution are respectable qualities.