If the light comes on or there is continuity, there is a short somewhere in the circuit. Using a battery or jump box, connect one end of the black test lead to the negative terminal and the other end to the “Ground” pin. Also asked, how do you test the ground on a trailer wiring? Then press the second probe against the last prong on the relay. If it still doesn’t work, you can also check to be sure if it’s a connection problem and not the wirin… If checking household receptacles and lighting for hot wires, the needle should read between 110 and 120 volts. Trailer wiring combines the left turn/brake and right turn/brake … If checking for hot wires on large appliance receptacles or built-in appliances such as, cook tops, ovens or water heaters, your meter should read between 240 to 250 volts. Set the multimeter to read voltage. The first test is a voltage test, which you perform with the multimeter set to measure AC voltage in the 200-volt range. I have attached a photo of the # BTMT15 and have noted where the test position is. Best of all, you don’t need to spend a fortune to get a good multimeter. A short-circuit should not be confused with an open circuit, in which current does not flow at all. Touch the black (negative) lead to bare metal on the vehicle. Now apply the same process to the other control pinholes. Set your multimeter to read volt DC, connect the black probe to the negative and the red probe to one of the control wires, if your trailer plug is in order, your multimeter should have a reading approximately equal to the volts of your battery. Look for broken or loose wiring insulation or damaged pins as … Lipscomb brings more than a decade of experience in the consumer electronics and advertising industries. How do you test an electric brake controller without a trailer? You're now going to test this length of the wiring harness for continuity, which shows whether electricity is able to flow through the wiring. Connect the positive wire to the positive red probe, and connect the black probe to a metal part of the car frame. A check for short circuits is one of the most basic tests you can perform with a multimeter. multimeter image by dinostock from Fotolia.com. NOTE: You'll be testing the circuits of the connector of the O2 sensor itself and not the O2 sensor harness connector (that's part of the engine wiring harness). Take the other probe and touch it to the other terminal on the motor. Check the reading on your multimeter face. David Lipscomb is a professional writer and public relations practitioner. Check out the white wire on the trailer to see if it's actually used as a ground (which it should be). Click to see full answer Tell your helper to turn on the left turn signal. Copyright 2020 FindAnyAnswer All rights reserved. Connect the second test lead to the positive terminal of the battery or jump box. Disconnect both ends of the harness slated for testing. Pull firmly on each end as if trying to stretch the wire. On the simplest meters, you use the resistance setting; sophisticated models have a continuity setting that flashes a light or beeps a tone to let you know a connection is a short circuit. 1. Tell your helper to shut off the turn signal and step on the brake. For example, pull out the plug on the back of the vehicle's in-dash radio. This is a must before installing a wiring harness onto anything. Take one of your multimeter probes and touch it to one terminal on the motor. Turn the switch to the "resistance" setting on the multimeter. If the light still doesn't come on, you know there is a problem with the wiring. Set the switch on the multimeter to "DC.". Touch the red (positive) lead to the wires in the harness that need to be tested. Have an assistant crank the engine for a few seconds while you watch the meter's readout. Wire harnesses are used to connect two or more items, using a series of wires in one bundle. Attach a 12-volt test light's ground clip to a bare metal portion of the trailer's frame. Click to see full answer Thereof, how do you test a trailer bulb? Plug the multimeter probes into the ports on the bottom of the machine so you can use them for testing. For this test we use Fluke 87-V multimeter which we buy on Amazon.com 1. How much does it cost to replace rod bearings? Conclusion If you wanted to understand how to test car fuses with a multimeter, reading through this article has provided you with some valuable insight into the steps you need to take. Lipscomb holds a degree in public relations from Webster University. You will find there are two terminals in the wiring harness, where the pongs on the injector inserts. Those 4 wires should be green, yellow,brown and white. Wire harnesses are used to connect two or more items, using a series of wires in one bundle. Set your digital voltmeter to a low range on the AC voltage scale. If there is a short, you will hear a beep. 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