How to Diagnose Parasitic Drain on Your Car Battery

There are few things more annoying than dead batteries. It’s inconvenient when you park a vehicle that’s in fine working order and it won’t start the next morning. Battery drain caused by parasites is a common cause of failure. Although it’s not dissimilar to what leeches do, the name gives it a nasty ring that’s not warranted. It happens when a little electrical current continues to run in your automobile even after you switch it off, gradually diminishing the battery’s power. This might result in your car not starting or abruptly stalling. Diagnosis and repair of a parasitic drain might be difficult, but with the correct equipment and expertise, it is possible.

But first, let’s look into what is a parasitic drain.

A parasitic drain on your car battery occurs when a little electrical current continues to run in your vehicle even after you switch it off, gradually reducing the battery’s power. This occurs when one or more of the vehicle’s electrical systems or components remain operational after the vehicle has been shut off and continues to drain power from the battery. This may include items like lights that have been left on, power windows that have not been turned off, or an auxiliary music system that has not been turned off.

If the parasitic drain continues unabated, the battery will ultimately drain entirely and the vehicle will not start. This may potentially cause the battery to fail and need replacement in rare situations. Furthermore, a parasitic drain might reduce the overall life of the battery, requiring you to replace it sooner than intended.

Here’s how:

  • Step 1: Start by turning off all of your car’s electrical components, including the lights, radio, and any other accessories.
  • Step 2: Set the multimeter to measure DC amperage, then connect the positive (red) and negative (black) leads to the positive and negative battery terminals.
  • Step 3: Measure the current going through your vehicle. A typical, healthy automotive battery should register less than 50 milliamps (mA). If the value is greater than this, it indicates that your battery is experiencing a parasitic drain
  • Step 4: To locate the cause of the parasitic drain, use the multimeter to test each individual electrical component in your vehicle. Begin by detaching the negative battery wire before taking a reading. If the reading falls, the detached component is the cause of the parasitic drain. If the reading does not change, go to the next component and continue the procedure until the culprit is identified.
  • Step 5: Once the cause of the parasitic drain has been discovered, you may either repair or replace the damaged component.

Common sources of parasitic drain include:

  • trunk light left on
  • A door switch that is not working properly
  • A malfunctioning power window motor
  • A faulty aftermarket audio system

Some things you can do to prevent parasitic drain:

  • Regularly check that all the lights, audio systems, car accessories, and so forth are turned off when you turn off the car.
  • Remove electronic devices that you don’t use or use infrequently.
  • Keep your car battery in good condition, ensuring that it is clean, properly charged, and securely fastened.
  • Use a battery maintainer to keep your battery charged if you plan to leave your car unused for extended periods.
  • Consider replacing any high-power consumption devices like aftermarket audio systems, car alarms, and other add-ons with more energy-efficient options.
  • Instead of leaving your car in “accessory” mode when you’re not driving it, make sure to turn it off completely to avoid any electronic devices or systems drawing power.

By following these steps, you can diagnose and fix a parasitic drain on your car battery, and keep your vehicle running smoothly. Remember to consult your car manual when checking and replacing the battery or if in doubt, call or WhatsApp us at 800-START (78278) for assistance, and book your battery replacement service.

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