How to Install a New Ground Wire

car wiring, hood up
A little wiring help can go a long way. Getty

Before you run a new ground wire to a malfunctioning electrical component, it’s a good idea to do lots of testing. For ground circuits, this isn’t too bad. But be sure you are getting good power to the circuit before you decide to rewire things.

There are two ways to run a new ground wire. Both operate on the same principal —- providing a new path for electricity to reach the car’s ground — but one is simpler, and should be explored first.

 

Simpler

If you’ve determined that you definitely have a ground wire in your electrical harness that is not grounded, go ahead and snip the wire, leaving as much length as possible on the component end of the wire. In other words, start at the electrical component (the window or the light that isn’t working) and work your way along the faulty ground wire as far as you can from the component. Snip the wire. Now look around to see if there are any other grounded wires near the component. You may have to remove some trim or pull some carpet up. A grounded wire will likely be the same color as your faulty ground, and will terminate in a screw or bolt that is attached firmly to the actual car at some point. If you don’t see an existing ground anywhere, you can test any screws or bolts you see near you with a circuit tester to see if they are good points for your new ground wire. If you test a screw or bolt and it turns out to be a good ground, you will attach a terminal end to the new wire and use the screw to hold it in place.

If the wire you snipped isn’t long enough, you can add some additional wire to get the length you need. I always try to use the same color wire for my extensions to avoid any future confusion when the car is being worked on. When running new lengths of wire, be sure to safely tuck the wires where they will not be pinched or pulled, and are safe from moisture.

 

Slightly less simple, but not bad.

If you’ve explored as far from the electrical component as you care to and have not found a suitable installation point for your new ground wire, you can make your own. Find a place on the car’s chassis that is near the electrical component that’s failed you. You may need to remove or pull back a section of carpet or trim to get to the metal. Get a self-tapping sheet metal screw and drill the appropriately sized hole in the car’s metal chassis. Clip the old ground wire leaving as much length as possible from the electrical component or plug to the point you make your cut. Strip the wire. Using a crimp-on terminal end, secure the ground wire to your new grounding screw. If your old wire does not have enough length to make it to your preferred ground screw location, it's fine to extend the wire using a crimped connection. Use the same color wire if possible to avoid any future confusion. 

With your new ground wire in place, you should be able to use the electrical component as you always did.