ElectricalSup_13

FleetMaintenance_NovemberDecember_2016

ELECTRICAL SYSTEMS DIAGNOSTICS Common causes of electrical system failures Which tools are the most effi cient to diagnose common vehicle electrical system issues? Electronic Specialties Fuse Buddy ONE OF THE MOST FRUSTRATING THINGS A TECHNICIAN COMES ACROSS when diagnosing a vehicle are intermittent issues. When the issues are on an electrical system, it becomes even more diffi cult to determine the root cause. We’ll cover some common issues technicians face when it comes to working on electrical systems. Enter 6 at “e-inquiry” on VehicleServicePros.com Enter 7 at “e-inquiry” on VehicleServicePros.com Enter 8 at “e-inquiry” on VehicleServicePros.com DECEMBER 2016 | ELECTRICAL TESTING SUPPLEMENT | 13 by Barry Hoyland , Contributing Editor, PTEN magazine Cal-Van Tools Amp Hound 2 Power Probe DMM Issue 1: Intermittent shorted or open circuits Intermittent short circuits usually manifest themselves by blowing a fuse. This can be benefi cial, as it gives you a starting point for your diagnosis. Obtaining both the power distribution and wiring diagrams will give you details of components and other possible areas of concern. Additional valuable pieces of information are TSBs and common fi xes that have been compiled by repair information sources such as AllData, Mitchell 1 or Identifi x. If there are no known common issues it may be more diffi cult to locate the root cause of the problem. Some possible sources of intermittent failures are connections with high resistance or loose connecting pins that cause the fuse to heat up and melt. Close inspection of connectors to see if there are signs of overheating such as discoloration of either the pins or the plastic housing is useful. In order to provide a quality repair, it will be necessary to replace the connector pins and the plastic housings on both sides of the connection. Other causes of intermittent shorts are components themselves. In this case, it may be helpful to measure the resistance within the component using a DMM. Another very effective test is to use an ammeter or other testers, such as the Cal Van Amp Hound 2 or the ESI Fuse Buddy, to measure the current the circuit is actually consuming. If the component is operated with a relay, it will be necessary to activate the relay using either a relay activation tool, a Power Probe or with bi-directional commands using your scan tool. The source of intermittent issues with either open or shorted wiring may be diffi cult to locate. In addition to TSBs, other tried and true methods to fi nd them are to physically move wiring harnesses and connections to recreate the problem. It may be helpful to place the vehicle in gear with the brakes applied while lightly accelerating. By doing this the engine, transmission, exhaust and attached components move and may pull on connections or wiring to recreate the issue. This may need to be done in forward and reverse to fi nd the cause of the short or open circuit. Using short/open circuit detection tools can be very valuable in determining the root cause of these problems. These tools work be transmitting a signal down the wire while using a receiver to determine where the signal changes or disappears. Continued on page 14 »


FleetMaintenance_NovemberDecember_2016
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