How to check wiring harness with multimeter

How to check wiring harness with multimeter. Electronic components in today’s vehicles mean that cables are laid virtually everywhere. But we don’t see them because it’s just unsightly and ruin the car’s stylish interior.

Instead, all of these cables are bundled in flexible plastic tubes and wire harnesses that traverse the vehicle through ducts along the sides, ceiling, and floor of the car, hidden behind panels, carpets, and upholstery.

How to check wiring harness with multimeter

Form  These harnesses pass through tight spaces and are exposed to the opening and closing of tens of thousands of side gates or tailgates, so there is a good chance that the wires in the bundle will break or shortly after the protective plastic cover wears out.  What is now fed by the broken or damaged wire no longer works when that happens.

Steps To Check Wiring Harness With Multimeter

Here we are going to use a multimeter in our process.

Use The Manual Multimeter kit

Use the repair manual or fuse box description to determine which fuse or relay is connected to a non-functional accessory. If multiple components are not working, use the schematic to find common ground in the circuit. This automatically isolates areas that need to be visually inspected and tested.

Check The Fuses

Next, make sure the fuse is blown, and there are no problems, and follow these tips to check the fuse with a test lamp. Connect the test light to the ground and test it to ensure it is illuminated from a suitable power source.

Check both sides of the fuse to ensure it is turned on if it is not always hot. When replacing a blown fuse, make sure the amperage of the new fuse is the same as the original fuse. Using a new fuse with a higher amperage can cause too much current in the circuit and damage the components.

Use Multimeter To On The Switch

If the wire is wrapped in a flexible plastic tube, carefully remove the box so that you can see and feel the wire.  Visually inspect each wire to find where the plastic cover is worn and bare copper wire is exposed. These are problem areas and need to be fixed. Use the multimeter by turning on the switch that powers the accessory. I’m checking my tension.

Negative Leads Of Multimeter

Connect the negative leads of the multimeter to good ground and connect the positive charges to the positive terminals of the non-operating vehicle accessory or the charges connected to it to see if the voltage is flowing through the addition. Confirm.

As long as you know the expected voltage of the circuit (12 V before load, close to 0 afterloads), the voltage drop test is an easy way to find short courses and breaks.

Division Of Circuits

Dividing the circuit into one-thirds helps to narrow down the course. Therefore, start by probing back with Tips from the battery to load, test the load, and try the ground side of the circuit.  To test the wire harness, first, disconnect the cable connected to the accessor to test the wire harness. Carefully trace the wire to the first connection point you come across.

This may require the wire to be removed from the protective plastic tube. Disconnect the wire at the first connection point found. Now test the continuity of the wire harness of this length. This will tell you if the current can flow through the wiring. Set the multimeter to the “Continuity” setting.

Check Multimeter Reading

Assuming there are multiple wires in the harness, insert the probe into one socket of the connector, return that one lead to the other end, and connect the other probe of the multimeter to that end or Connect If the multimeter reading is infinite ohms or OL (out of limit), it indicates that the circuit is electrically open and that this section of the cable is likely to be defective.

Repeat The Process

Repeat this process for the other wires in the harness until the faulty section is identified. If all the wires in the harness are okay, then there may be a problem in the untested section of the harness between the accessory and the power supply.

Once a faulty cable is identified, either remove the defective section and connect a new wire or replace the entire harness section with a new one to repair the line.


We have discussed everything about the wiring harness with a multimeter. By following some of the steps like using the multimeter kit and checking the fuses, and then by checking multimeters reading, you can fix your problem independently.

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