Tool Briefing Tests New Start/Stop www.VehicleServicePros.com MAY 2016 PROFESSIONAL TOOL & EQUIPMENT NEWS 53 MINI-DUCTOR® II Heats and releases frozen parts faster and more safely than a torch. Ask your local tool professional for a live demonstration. miniductor.com TM ® Circle 196 on card, or enter at “e-inquiry” on VehicleServicePros.com Call 800-227-1603 for more info. - www.esitest.com New Item! Batteries 726 Digital Battery & Electrical System Analyzer with Printer 1) Tests both EFB & AGM flat plate Start/Stop batteries. 2) Also tests Regular, AGM flat, AGM spiral & VRLA/GEL starting batteries. 3) Complete program- med test of the starting & charging system. 4) Print test results for permanent records & cust. relations Circle 197 on card, or enter at “e-inquiry” on VehicleServicePros.com 6 LOCATE AND REPAIR THE SHORT We have two separate issues; one is a short in the trailer running lamp circuit, which is easiest, and may lead us to the other problem. The easiest tool we have found to locate a short is the Power Probe ECT2000. This tool uses a transmitter to send a signal through a circuit and a receiver that will capture the signal (see Fig. 3). The receiver is used to follow the wiring and show the loss of signal just at the point of a short. The tool also can be used to find open circuits in a similar fashion. Using the tool, we located a short in the wire going to the left taillight of the trailer. We repaired the wire that had been damaged from a screw rubbing the wire and had no further issues with the blown fuse (see Fig. 4). We still had the battery drain and needed to find its cause. It seems unlikely that the trailer brake control module could have an issue that would cause a battery drain without having a trailer connected, but the GM system uses a relay that uses battery power to supply voltage to the trailer brake module. Without a trailer connected, there would be no reason for the system to draw current unless the relay itself was faulty, not allowing the relay to open when it’s operating signal was not present. Using Mitchell 1’s ProDemand, we found the brake control relay and module were located above the spare tire under the truck. After we removed the spare tire, we were able to locate the relay and disconnect it. After disconnecting the relay, the Amp Hound 2 was reconnected and confirmed the current draw was no longer present. With no current draw, we focused on why the relay was activated. Checking the wiring with the Power Probe IV, there was voltage present from the battery and a good ground. With the engine running, there was not a signal present at the relay control, so it appears that the fault is the relay itself having an internal issue causing it to stay energized once it had been engaged. We replaced the relay and reinstalled the spare tire. After verifying there was no current draw, we had the customer drive the vehicle and trailer to confirm the issue did not return. Solving what turned out to be multiple electrical issues can be intimidating, but using the right tools can make it much easier and profitable. Fig. 4. We repaired the wire that had been damaged (shown here), due to a screw rubbing the wire. After repair, we had no further issues with the blown fuse.
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