The customer's complaint is simple: the volt gauge is reading low. The fix seems just as simple: replace the alternator.
Except on a lot of modern vehicles, nothing is wrong. Smart charging lets the control system change alternator output based on operating conditions, so a reading well below 14 volts can be exactly what the vehicle commanded. Many customers just aren't used to seeing it.
That's one reason Erik Screeden says alternators get replaced unnecessarily every day. In this Tech Tip Short, he walks through the rest. A weak or incorrect battery stresses the charging system and can damage the new unit. Excessive resistance can sit on the positive or ground side. A worn belt or weak tensioner can cause belt slip. And a parasitic draw can keep the system working after shutdown.
His question for every alternator job isn't "did it fail?" It's "what caused it to fail?"
Watch this Tech Tip Short before your next install. Then visit https://www.waiglobal.com/us_en/videos to watch more technical videos from WAI Global.
About the Author
Erik ScreedenErik Screeden
Technical and Multimedia Content Director
Erik Screeden is the Technical and Multimedia Content Director for the Vehicle Service & Repair Group. Erik is an ASE Master Automobile Technician with L1, and L4 credentials, who has been in the industry for over 25 years in various capacities. During that time, Screeden was a technician. He started out at a Ford dealership and continued to several independent repair facilities as well as spent time in the specialty aftermarket at a GM-specific performance shop. After his time as a technician came to an end, Screeden transitioned into a role providing scan diagnostic and J2534 tool support. He was then able to parlay his experience as a technician and a support specialist and use that in several technical sales roles.
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