How to Rewire a Car In a Safe Way

The electrical wiring system of a car is probably the most neglected maintenance task. Most car owners worry about the engine, tires, fuel, and other parts. Even cleaning and washing get more priority than the wires. But the truth is that all electrical parts function because of the wiring network. So, it’s important to know how to rewire a car and do that safely.

Rewiring a car takes time, patience, and skills. It’s better to have some prior experience because it’ll be too complex for a noob. It will be better if you can plan the whole process beforehand and draw an outline of the electrical wiring system.

How to Rewire a Car Safely

When you think about how to rewire a truck or car, you should strictly follow the guidelines to get the job done quickly and without an accident. Follow these steps to keep both yourself and those around you safe while rewiring your car:

Turn off the car’s power

Before starting, turn off the power and make sure all devices are disconnected. Next, disconnect the battery cables by loosening the bolts on their nipples before removing them from their respective terminals. When they’re removed, set them aside securely so they won’t touch each other or any exposed metal parts.

Now remove any of the additional wires that are connected to the battery terminals. Cover them with insulating tape and set them aside.

rewiring a car
Collect all wiring harnesses and label them. (Credit: Crutchfield)

Cut the main wiring harness

Locate the main wiring harness in the engine bay (it should be routed through its own rubber grommet). Cut it between the engine bay and where it enters your cabin, then pull all of the old wires out of their grommets on either side. Make sure you don’t accidentally cut any other wires.

Strip off the wires

Strip off about a centimeter or so from each wire end and attach a numbered label to each one. You may find having a multi-way crimping tool handy for this part — especially if there are lots of different colors involved.

Reattach the wires

From here on, things get a bit more technical, and you’ll need to refer to your owner’s manual. But the basic gist is that you should re-attach the wires in order, so it all makes sense, and then connect them back up where they came from.

Once everything is reconnected, press each wire securely into its grommet before putting things back as they were (battery cables, etc.). This will take a bit of time because of all the crimping involved, but don’t rush it because rushing things can lead to mistakes.

Test the wiring

Finally, turn on your headlights and make sure there are no illuminated warning lights on your dashboard. If any still exists after starting the engine, shut off at once and go back through everything again until you fix whatever problem is suspected.

If all is well, turn on your headlights again and check that the electrical system is functioning correctly. Any problems here are likely to be related to faulty wiring or connections. So, you’ll need to go back through everything and re-check everything for errors.

Finish the task

This is the last step of how to rewire a car. Replace any of the trim panels in opening access to the engine bay area (side skirts, for example). After, put things back as they were and closing the opening.

You can buy secondhand OEM wire harnesses for a lot less than what they would cost new. As long as it’s still in good condition, this can be a much more cost-effective solution. But if your existing wiring has been damaged by corrosion or burned through, it’s important to replace it as soon as possible. If handled properly, your car will be safer and you won’t have to worry about emergency repairs for a long time.


How Much Does It Cost to Rewire a Car?

The cost to rewire a car will vary depending on the type of vehicle, but it typically ranges from $1,200 to $1,500. The average cost is about $1,350. Get quotes for more than one business to see the price differences. If one demands a higher price, ask them to explain the procedure.

The car rewiring cost can vary so much because labor costs can be anywhere from 50% up to 80%. If there are other problems with the electrical system or engine that need attention as well, then those parts may also affect how expensive your service will be. So, it’s quite difficult to give an exact figure of how much to rewire a car but be ready to spend at least $1,000 for a decent job.


So, this is how to rewire a car safely. For those who have never worked with cars before, follow instructions carefully according to your owner’s manual. Doing so will save parts from damage. If you keep seeing warning lights after restarting the engine, you might have done something wrong. In that case, take the car to a servicing shop for fixing the problem.