How to Replace a Muscle Car Wiring Harness

January 27, 2012

For the most part, replacement of the muscle car wiring harness is a plug and play operation, and is a quick task that can be completed within a couple of hours. Most older domestic vehicles have two wiring harnesses: one for the headlights, turn signals, brake lights, and interior and dash lights, and one for the engine compartment and engine components. Over time, the wiring within the wiring harness can become brittle and will break, damaging connections and interrupting the signals sent to different components. Due to the location of the wiring harnesses, they are exposed to extreme temperatures, making them very susceptible to weatherization and decay. Here's how to replace the wiring harnesses.

Step 1: Locate the New Wiring Harnesses

You can find the exact wiring harnesses needed for your particular make and model in a variety of ways. You can order them online, or obtain the needed harness from most auto parts stores. By ordering the harness from the auto parts store, you have someone on site who can evaluate your particular vehicle and make specific recommendations for your needs. For the most part and for typical operation of your specific vehicle however, the wiring harnesses are universal.

Step 2: Locate the Existing Wiring Harness

The wiring harnesses will typically plug into receptacles on the driver's side of the engine compartment, against the firewall. The wiring harness looks like a bundle of wires, usually wrapped in black plastic. The exact location may vary, but they are specific in that they plug into receptacles at both ends of the wiring.

Step 3: Remove Old Wiring Harness

Again, for the most part, this is usually a matter of pulling the plug. Many wiring harnesses snap into the receptacle, locking into place. You may need to squeeze on the connection that you are removing to disengage it from the locking mechanisms on the receptacle.

Step 4: Install New Harness

The wiring harness usually can only be plugged into the correct receptacle. The shaping of the connectors are specific to which harness you are working with. The wiring will most likely be color coded so that all you have to do is match the shape of the connections or the colors of the wiring. Many harnesses have a rubber boot at one or both ends. You will want to make sure that this is reinstalled to the position of the original harness, and if needed secured.

Step 5: Test All Connections

Once the new harnesses are installed, test all the electrical components that are dependent on them. Sometimes it's helpful if you have an extra person to stand outside the vehicle and let you know when the blinkers, tail lights and any other controls or components come on and off. Start the car and turn on all the controls inside the vehicle. Make sure all components that are dependent on the electrical system are functioning.