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2017 Sonata Limited: Battery dies overnight, possible parasitic draw?

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James R. · rep 0 · May 22, 3:01 AM · 1 replies · solved · Question

Vehicle: 2017 Hyundai Sonata Limited

Hello everyone,

I'm having a persistent issue with my 2017 Hyundai Sonata Limited. The battery keeps dying overnight, or sometimes after just a couple of days of sitting. I've replaced the battery twice in the last year, and the alternator was checked and seems fine. It charges okay when the car is running.

It feels like something is draining the battery when the car is off. I don't have any aftermarket accessories, and I'm careful to turn off all lights. Could this be a parasitic draw? How can I even begin to figure out what's causing it?

Any advice on how to track this down would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:01 AM

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ClearTheCode admin answer:

It definitely sounds like your 2017 Hyundai Sonata Limited is suffering from a parasitic draw. This occurs when an electrical component continues to draw power from the battery even after the vehicle is turned off, leading to a dead battery over time. Since you've replaced the battery and checked the alternator, a draw is the most likely culprit.

Here's how you can approach diagnosing a parasitic draw:

  1. Charge the Battery Fully: Start with a fully charged battery to ensure accurate readings.
  2. Prepare for Testing:
    • Ensure all doors are closed, lights are off, and the ignition is off.
    • Wait at least 15-30 minutes after turning off the car for all modules to 'go to sleep.' Modern cars have many modules that stay active for a short period after shutdown.
  3. Perform a Parasitic Draw Test (with a Multimeter):
    • Disconnect the negative battery terminal.
    • Set your multimeter to measure Amps (A) or milliamps (mA).
    • Connect the red (positive) lead of the multimeter to the disconnected negative battery cable.
    • Connect the black (negative) lead of the multimeter to the negative battery terminal.
    • The multimeter is now in series, measuring the current draw. A normal draw should be around 20-50 mA (0.02-0.05 Amps). Anything significantly higher indicates a problem.
  4. Isolate the Circuit: If you have a high draw, start pulling fuses one by one from the fuse box (both under the hood and inside the cabin), while watching the multimeter. When the amperage drops significantly, you've found the circuit responsible for the draw. Consult your owner's manual to identify what components are on that circuit.

Common Causes of Parasitic Draw:

  • Faulty Modules: A module (e.g., radio, body control module, navigation unit) that isn't properly shutting down.
  • Stuck Relays: A relay that remains energized when it shouldn't.
  • Interior Lights/Trunk Light: A light that stays on due to a faulty switch.
  • Aftermarket Accessories: While you mentioned not having any, sometimes even a poorly installed dash cam or alarm system can cause a draw.

When to See a Shop: If you're uncomfortable performing the multimeter test, or if you've identified a circuit but can't pinpoint the exact component (e.g., a circuit with multiple modules), it's best to take your Sonata to a professional mechanic. Diagnosing parasitic draws can be time-consuming and requires patience and a good understanding of automotive electrical systems. A shop can use advanced diagnostic tools to isolate the exact component causing the drain.

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