Skip to main content
Sister Publication Links
  • Automotive News
  • Rubber News
  • European Rubber Journal
Subscribe
  • Login
  • Register
  • Subscribe
  • Current Issue
  • Global Tire Report
    • ADAS
    • MID YEAR REPORT
    • TIRE MAKERS
    • COMMERCIAL TIRE
    • GOVERNMENT & LAW
    • MERGERS & ACQUISITIONS
    • OPINION
    • SERVICE ZONE
    • BEST PLACES TO WORK
    • OBITUARIES
  • HUMANITARIAN
  • Data
    • DATA STORE
  • Custom
    • SPONSORED CONTENT
  • Resources
    • ADVERTISE
    • Events
    • AWARDS
    • CLASSIFIEDS
    • DIRECTORY
    • SHOP FLOOR
    • ASK THE EXPERT
    • LIVESTREAMS
    • WEBINARS
    • SEMA LIVESTREAMS
    • RUBBER NEWS EVENTS
    • Best Places to Work
    • BALANCING
    • DEMOUNTING
    • SAFETY
    • TIRE REPAIR
    • TPMS
    • TRAINING
    • VEHICLE LIFTING
    • WHEEL TORQUE
  • DIGITAL EDITION
MENU
Breadcrumb
  1. Home
  2. Service Zone
March 05, 2019 01:00 AM

Unpleasant consequences of disconnected battery

Dan Marinucci
  • Tweet
  • Share
  • Share
  • Email
  • More
    Marinucci

    Disconnecting a vehicle's battery may create costly, unpleasant surprises for tire dealers and service shop operators.

    In this column and my next one, I'll discuss the potential pitfalls of battery disconnect and recommend sensible precautions.

    Blithely detaching a battery cable or cables may erase memory — commonly called learned values — which on-board computers have accrued during normal driving.

    When these values are erased, a vehicle may run poorly after a technician reconnects the battery cable(s). Worse yet, a technician and/or shop foreman may not realize why the car runs worse than it did when it arrived.

    Remember that re-establishing these learned values could require considerable road testing.

    Usually it's difficult to charge for this additional time on any given repair job. Plus, demanding the additional time may look suspicious to the car owner.

    However, the costliest aspect of this procedure may be the fact that it upsets your service department's already-tight appointment schedule.

    For openers, proper procedure for certain repairs dictates disconnecting the vehicle's battery first. Naturally, disconnecting one or both battery cables shuts down the entire electrical system — including all the vehicle's on-board computers.

    Years ago, there were only two adverse effects of disconnecting a battery. First, a technician had to reset the clock on the dashboard.

    Second, he had to reset the station selections on a customer's electronically tuned radio. But electrical systems aren't quite that simple today.

    For example, the more-common vehicles that your techs service these days may have a multitude of on-board computers.

    The greater the number of computers, the greater the potential risk of losing learned values after a battery's disconnected.

    What's more, it's likely that your tire dealership or service shop repairs a fairly wide range of vehicles. Experience has shown that it's difficult to predict which computers on which vehicles a disconnected battery affects.

    Sometimes, disconnecting a battery may cause a rough or unstable idle; it also could cause stalling because the idle speed is abnormally low.

    In other cases, disconnecting a battery affects transmission functions, causing symptoms such as late and/or harsh shifts.

    Equally distressing are trouble codes that appear in systems such as ABS, traction control and stability control after a battery disconnect.

    Also, I have seen cases where battery disconnect disrupted operation of "automatic-down" power windows.

    Tire Business photo by Dan Marinucci

    The greater the number of computers, the greater the potential risk of losing learned values after a battery's disconnected.

    Technicians and shop foremen may struggle with these issues simply because they don't associate the new-found problems with a recent battery disconnect.

    Another potential complication is that some consequences of battery disconnect may not appear until a tech road tests a vehicle.

    Unfortunately, some bosses don't enforce routine post-repair road tests.

    Therefore, the customer discovers those symptoms on the drive home. Good luck explaining what happened.

    In all fairness to this topic, some vehicles' computers relearn so quickly that no one notices anything unusual after a battery disconnect.

    However, this trait may foment a sense of false security for techs who disconnect batteries without considering the potential consequences.

    It's imprudent to assume that all computers re-learn values promptly. In fact, a tech may have to drive a vehicle for 30 minutes or more — at various road speeds and engine RPM — to finish the job.

    Personally, I stopped predicting the time needed to relearn normal values. (I call the process complete when, for instance, the idle speed is smooth and the automatic transmission shifts normally again.)

    In my next column, I'll discuss how to prevent memory loss by connecting auxiliary power to a vehicle before someone disconnects its battery.

    Letter
    to the
    Editor

    Do you have an opinion about this story? Do you have some thoughts you'd like to share with our readers? Tire Business would love to hear from you. Email your letter to Editor Don Detore at [email protected].

    Most Popular
    1
    USTMA: Demand for passenger tires grew in 2023
    2
    Passenger tire imports up in Q3 but LT, TBR drop
    3
    Yokohama unveils ‘extreme traction' truck tire for snow, ice
    4
    Tire Business ranks the Top 75 Tire Makers of 2023
    5
    Kumho set to launch Solus all-weather passenger tire
    SIGN UP FOR NEWSLETTERS
    EMAIL ADDRESS

    Please enter a valid email address.

    Please enter your email address.

    Please verify captcha.

    Please select at least one newsletter to subscribe.

    Newsletter Center

    Staying current is easy with Tire Business delivered straight to your inbox.

    SUBSCRIBE TODAY

    Subscribe to Tire Business

    SUBSCRIBE
    Connect with Us
    • Facebook
    • LinkedIn
    • Twitter
    • Instagram
    • RSS

    Our Mission

    Tire Business is an award-winning publication dedicated to providing the latest news, data and insights into the tire and automotive service industries.

    Reader Services
    • Staff
    • About Us
    • Site Map
    • Industry Sites
    • Order Reprints
    • Customer Service: 877-320-1716
    Partner Sites
    • Rubber News
    • European Rubber Journal
    • Automotive News
    • Plastics News
    • Urethanes Technology
    RESOURCES
    • Advertise
    • Privacy Policy
    • Privacy Request
    • Terms of Service
    • Media Guide
    • Editorial Calendar
    • Classified Rates
    • Digital Edition
    • Careers
    • Ad Choices
    Copyright © 1996-2023. Crain Communications, Inc. All Rights Reserved.
    • Global Tire Report
      • ADAS
      • MID YEAR REPORT
      • TIRE MAKERS
      • COMMERCIAL TIRE
      • GOVERNMENT & LAW
      • MERGERS & ACQUISITIONS
      • OPINION
      • SERVICE ZONE
      • BEST PLACES TO WORK
      • OBITUARIES
    • HUMANITARIAN
    • Data
      • DATA STORE
    • Custom
      • SPONSORED CONTENT
    • Resources
      • ADVERTISE
      • Events
        • ASK THE EXPERT
        • LIVESTREAMS
        • WEBINARS
        • SEMA LIVESTREAMS
        • RUBBER NEWS EVENTS
      • AWARDS
        • Best Places to Work
      • CLASSIFIEDS
      • DIRECTORY
      • SHOP FLOOR
        • BALANCING
        • DEMOUNTING
        • SAFETY
        • TIRE REPAIR
        • TPMS
        • TRAINING
        • VEHICLE LIFTING
        • WHEEL TORQUE
    • DIGITAL EDITION