How to Use Circuit Tester and Multimeter to Confirm Lighting Functions on Vehicle Wiring

Published 11/21/2018

Products Featured in This Question

16 Gauge Primary Wire - Black - Per Foot

(60)

$1.14

Digital Multimeter with 42" Long Test Leads - LED Display

(2)

$21.55

LCD Digital Circuit Tester

(23)

$26.31

Question:

Which is the hot wire and which is the ground and the car is green white and black and green and white mixed which of the wires is the hot on the car Mitsubishi lancer es which do I hook up the red green or the mixed green and the white is a ground. On aftermarket spoiler u have a red wire and white wire.

asked by: John C

Expert Reply:

Trailer wire colors sometimes follow a color code but there is never a guarantee that this is done all the time. When a vehicle assembly line runs out of one wire color, they do not stop production - they change wire colors! More often than not, a white wire is ground, but there is no way to actually look this up reliably for your Lancer.

So the best way to figure out the correct wiring for installing an item like an aftermarket spoiler with built-in lighting functions is to test the car's wires with a circuit tester like # PTW2992 or a multi-meter like # PT89ZR. If you ground the tester or meter to the vehicle you can then test the wires one at a time until you find the one that is hot. You can refer to the linked video for an example of how the tester will react to a signal.

This testing is easiest if you have a helper who can activate the various lighting functions on the car, one at a time, while you test the wires. For instance, have him or her turn on the headlights while you test each vehicle wire; then test while the brake pedal is pressed, etc. This will help you confirm which function is carried on each wire.

expert reply by: Adam R