Hi all,

I’m dealing with a long-term battery drain issue on my car and I’m honestly running out of ideas. I’d really appreciate any advice or similar experiences.

Car:
Skoda Octavia Mk3 (2015), 1.6 TDI
Bought in 2016 with ~160,000 km

---

Problem

The battery keeps draining randomly. It has happened 3 times in the last 2 weeks, but it’s been an ongoing issue for a longer time.

Important detail:

• The issue did NOT happen when I first got the car

• It started after a few years of ownership

• It has happened on multiple batteries

• It even happened on the current battery shortly after it was new

---

Battery

• Current battery: Banner, ~2 years old (correct spec)

• Charging system tested → OK

---

Usage

• Car is used daily

• Mostly short trips now, but the issue also occurred when driving ~100 km daily

---

What we’ve already checked

1. Cooling fan suspicion

• Radiator fan sometimes ran 20–30 minutes after shutdown (very loud, full speed)

• Fan was completely disconnected for testing → battery still drained

So fan is likely NOT the cause.

---

2. Charging system

• Checked in service → OK

---

Other possibly relevant details

• Car is second-hand (unknown modification history)

• Zeder mechanical immobilizer installed (with electronic buzzer)

• FM Bluetooth transmitter (always unplugged after driving)

• Retrofitted multifunction steering wheel:

  • buttons don’t work

  • likely not properly connected / coded

• License plate light issue (one not working properly)

• Constant tire pressure warning (probably unrelated)

---

My suspicion

I’m thinking it could be:

• Parasitic drain from aftermarket electronics (GPS tracker, old alarm, etc.)

• Something that doesn’t go to sleep properly

• Wiring issue from previous owner

---

Next step planned

• Measure parasitic draw after the car goes to sleep

• Pull fuses one by one to isolate the circuit

---

Questions

1. Has anyone experienced something similar on Octavia Mk3?

2. Any common modules or known issues that cause battery drain?

3. Could the Zeder or partially connected multifunction steering wheel realistically cause this?

4. Any typical locations where hidden GPS trackers / aftermarket modules are found?

---

Thanks a lot for any help 🙏
This one is driving me crazy.

I would begin with the aftermarket immobiliser. Often they are hateful little things and sometimes incorrectly installed. But I see your Zeder is just a mechanical device so cannot be part of your issue except for the buzzer. Try disconnecting that.

Then my first step would be the correction of your faulty steering wheel.

Your parasitic draw suggestion is the right one. But it seems to be intermittent. As far as aftermarket GPS trackers are concerned, you should be looking for any extra wires or piggyback connectors. Easy to say, hard to do. Favourite locations for these would be the fuse and relay blocks.

Good luck.

Hello, welcome to the forum.

^^^ the above, plus Is the infotainment system original - or aftermarket?