How to Wire Glow Plugs

The glow plugs in a diesel engine are an important part of the system. Glow plugs are capable of heating the air inside the combustion chamber, causing the diesel fuel to explode upon injection inside the chamber. The combustion process moves the pistons, which, in turn, results in forward motion of the car. A slight malfunction in the glow plugs might cause excessive engine vibration, smoke, or loss of performance. It would be best to replace the glow plugs according to the specifications of the manufacturer and have them wired properly for better overall performance.

Materials Needed:

  • Hand gloves
  • Wrench or socket wrench set
  • Glow plug controller
  • Glow plug wire harness
  • Cotton rag

Step 1 – Open the Hood

Park the car on level ground, and work in a well lit area. Pop open the engine bonnet, and put on a set of hand gloves. Remove the negative connection of the battery, followed by the positive side. Locate the glow plug controller by following the wires that run from each combustion chamber in the engine to the location where the glow plug controller is located. The wires that run from the engine to the controller are the glow plug wire harness.

Step 2 – Remove the Wiring Harness

Remove the glow plug wiring harness carefully by pulling the harness from the controller. The wire harness may be held by a small lock, so be sure to press on the lock before pulling the wire harness. Do not remove the connection from the corresponding glow plugs in the engine.

Step 3 – Remove Glow Plug Controller

Use a wrench or socket wrench to loosen the bolts and remove the glow plug from the engine bay, and turn it in a counterclockwise direction. Set the mounting bolts aside. Grab the engine controller with your hand, and disconnect the battery cable nut attached to the controller.

Step 4 – Install New Glow Plug Controller

This is one of the most important steps when wiring glow plugs, as the glow plug controller will be responsible for the performance of the glow plugs. Attach the battery cable to the glow plug controller, and tighten the nut. Align the controller to the mounting holes where the old controller was located, and fully insert the bolts. Tighten it sufficiently using a socket wrench.

Step 5 – Install a New Wiring Harness, and Wire the Glow Plugs

Grab the new wiring harness and attach it to the new controller. Locate which wire is connected to a glow plug in the engine bay. Remove the old glow plug connection, and connect the new wire. Follow the same procedure for all the glow plug wires, and discard the old wiring harness. Make sure to do this right the first time to avoid engine problems upon starting.

It is easy to learn the process on how to wire glow plugs, but attention to detail is required for a successful DIY project. A diesel engine will run quieter and smoother with proper glow plug wiring.