FAQ
TL;DR: A 6.3A draw can roast a battery fast; “a meter on the 20A range shows 63A” is a misread—measure correctly first. [Elektroda, spinacz, post #16979967]
Why it matters: This FAQ helps Skoda Octavia II owners diagnose and fix parasitic drain, especially after radio or alarm changes.
Quick Facts
- Reported quiescent draw case: 0.63A about 2 minutes after locking (“sleep”). [Elektroda, mateusz1065, post #16981824]
- Suspect fuses observed: 12→0.6A, 15→0.18A, 23→0.5A, 24→0.3A (case data). [Elektroda, mateusz1065, post #16979948]
- Aftermarket items present in case car: alarm leads and a CB radio. [Elektroda, mateusz1065, post #16981824]
- Radio retrofit kept modules awake; adding a module and programming cured the drain. [Elektroda, pompon78, post #17355798]
- Expert advice: take the “first measurement of current on a dormant car,” not immediately after reconnecting. [Elektroda, spinacz, post #16980200]
Why is my Octavia II battery draining with 0.63A draw?
A 0.63A quiescent draw is excessive. The thread cases point to awake modules, aftermarket alarm/CB wiring, or radio retrofit issues. Start by confirming the current once the car is fully asleep, then isolate using fuses. Focus on circuits showing measurable draw, like fuses 12, 15, 23, and 24 in the case data. [Elektroda, mateusz1065, post #16979948]
How do I measure parasitic draw correctly on a dormant car?
Close doors, lock the car, and wait for sleep. As one expert put it, “The first measurement of current on a dormant car.” Use a series ammeter at the battery negative, without waking modules. If you reconnect power, allow the current to settle before reading. [Elektroda, spinacz, post #16980200]
Which fuses should I check first for unexpected current?
Use data from the case: fuse 12 showed 0.6A, fuse 23 0.5A, fuse 24 0.3A, and fuse 15 0.18A. Pull and replace one at a time to see which circuit drops the draw. Log each change to identify the guilty circuit. [Elektroda, mateusz1065, post #16979948]
Could aftermarket alarms or a CB radio cause battery drain?
Yes. The OP’s car had thin alarm wires on the battery strip and a CB radio. Such add-ons can keep modules awake or add constant loads. Temporarily disconnect non‑OEM devices to test. If current drops, rewire through ignition-switched power or use proper CAN‑aware interfaces. [Elektroda, mateusz1065, post #16981824]
My car shows 0.63A after 2 minutes. Should I wait longer?
Yes. Two minutes may be too short for all modules to sleep. Wait until current stabilizes at its lowest value before diagnosing. Avoid opening doors or waking the network during tests, or the reading becomes invalid. [Elektroda, spinacz, post #16980221]
I changed the radio and now the battery dies. Is the radio the culprit?
Likely. A newer head unit can prevent sleep if the CAN gateway is incompatible or coding is wrong. One case improved after fitting a module and programming. A specialist can code the gateway or add the correct interface. [Elektroda, pompon78, post #17355798]
What is a CAN bus and CAN gateway on the Octavia II?
CAN bus is the car’s data network linking modules. The CAN gateway routes messages and controls sleep. If the gateway is older than a retrofitted radio, the radio can keep the network awake, causing drain. [Elektroda, spinacz, post #17347301]
Do I need coding after a radio retrofit?
Often, yes. A “badly coded gate” can keep the car awake. Proper coding aligns the gateway and radio so the network sleeps when locked. Ask a VAG specialist to scan, code, and verify sleep status. [Elektroda, spinacz, post #17347327]
What fixed a confirmed Octavia II parasitic draw in this thread?
A user resolved the drain by inserting a module and uploading the correct program for the retrofitted radio. After that, the battery stopped discharging overnight. [Elektroda, pompon78, post #17355798]
Is reading 63A on the 20A meter range possible here?
No. That’s a misinterpretation. As the expert warned, “a meter on the 20A range shows 63A” is wrong; expect values like 6.3A or lower. Confirm your meter range and decimal placement. [Elektroda, spinacz, post #16979967]
How long should I wait after reconnecting the battery before trusting the reading?
Wait until current falls to the steady, low “sleep” value. Immediate readings reflect wake‑up activity. Measure only after modules sleep, per expert guidance. [Elektroda, spinacz, post #16980200]
Can a mechanic code the gateway to fix drain after a radio change?
Yes. The advisor noted the problem can be a “badly coded gate.” Correct coding or an interface module can restore proper sleep behavior and stop the drain. [Elektroda, spinacz, post #17347327]
Any quick 3‑step method to isolate the parasitic circuit?
- Measure quiescent current after the car sleeps.
- Pull one fuse at a time; note current change.
- Identify the circuit with the largest drop and inspect devices on it. [Elektroda, mateusz1065, post #16979948]
Should I inspect under‑hood relays or only cabin fuses?
Check both. The OP asked about under‑hood fuses, and add‑ons often connect at the battery. Inspect any non‑OEM leads first, then proceed to fuse isolation. [Elektroda, mateusz1065, post #16981824]
When should I stop and call an auto electrician?
If readings are unclear, wiring looks modified, or you’re unsure how to measure safely, seek help. One member warned that incorrect testing risks damage or fire. Safety and correct diagnosis come first. [Elektroda, yogi009, post #16981860]
What’s an example of an edge case that keeps current high?
A newer OEM radio on an older CAN gateway can prevent network sleep. The fix may require adding a compatibility module and programming, not just pulling fuses. [Elektroda, pompon78, post #17355798]
