Auto Service Professional

OCT 2018

Magazine for the auto service professional

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40 A S P O c t o b e r 2 018 E l e c t r i c a l S y s t e m F a i l u r e s So we know that resistance and heat are big contributors for electrical problems. Another well-known source for problems to crop up is water. Water and electricity don't get along very well. I was called to a shop for a 2006 Chevrolet Trailblazer that had an issue with the door chime going off randomly. Aer checking the circuit completely and reviewing the scan data in the truck's body control module (BCM), I didn't see anything out of the ordinary. I did however see the BCM register that the module was active when it did go off, but nothing else. I instructed the shop to replace the warning chime module and to save the old one for me. ey replaced the warning chime module assem- bly and the problem was cured… for now. I opened up the chime module and I imme- diately saw the cause of this component's failure. Water intrusion entered inside this module and caused corrosion on some of the circuits (see Figure 9). I called the shop and told them to get the customer back in and check for a water leak around the windshield, door and cowl assembly. ey did, in fact, find the water leak and re- paired the root cause of the module failure. Remember, it's very important to find the cause of any failure to avoid a repetition of the problem. When tracking down electrical circuit problems there are many things to take into con- sideration. e most important thing to consider is that you have to know how the circuit that you are troubleshooting works. You need to have access to a wiring diagram and you need to understand how that circuit runs and what that wiring dia- gram is telling you. e diagram is your road map. I don't for the life of me understand how some technicians can trace a circuit and get away with- out one. Another vital piece of the electrical trou- bleshooting puzzle is to have a good working DVOM and a complete understanding on how the meter works. Some meters are very sophisticated and have a lot of bells and whistles. at's fine as long as you're familiar with them. Also, a good set of test leads is equally im- portant. If you are using a bargain-priced test lead set, it's likely that the leads will already have some built-in resistance. is extra resistance will skew your readings and quite possibly give you a false direction on your test procedures. And finally, you have to have a good under- standing on how voltage, amperage and ohms work. Learning this may seem boring to some, but it is really important that you do understand it. With your knowledge in place and your tools in hand, becoming a skilled electrical troubleshooter will help you in tracking down electrical system failures in today's modern vehicles. ■ Figure 9: Water entered this module, caused by a leaking through an exterior source. Initially the blame was placed on the module. Edwin Hazzard owns South East Mobile Tech in Charleston, S.C., which is a mobile diagnostic and programming service providing technical service to many automotive and body repair shops. He has 35 years experience in the automotive industry. He currently is an automotive trainer, a board member of TST (Technician Service Training), a member of the MDG (Mobile Diagnostic Group), a member of the Professional Tool and Equipment advisory board for Pten magazine, a committee member of Nastaf, and is a beta tester for multiple tool makers.

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