Yes, a factory-installed car alarm can drain your car battery, but it's typically a minimal drain under normal conditions. The primary cause is parasitic draw, which is the small amount of battery power used by electronic systems when the car is off. A healthy factory alarm system should draw between 20-50 milliamps (mA). Problems arise when this draw exceeds 50-100 mA due to a malfunction, which can drain a battery in days or even overnight.
The alarm system has components like the siren, shock sensors, and the control module that remain in a low-power standby mode to detect threats. If any of these components develop a fault—such as a faulty sensor, wiring issue, or a module that fails to "sleep" properly—the parasitic draw can spike. Other common culprits that add to the drain include aftermarket accessories incorrectly installed or a weak battery that can't handle the normal draw.
To prevent this, have your battery tested regularly, especially if the car will be parked for extended periods. If you suspect a drain, a simple test with a multimeter can measure the parasitic draw. Disconnecting the battery for long-term storage is a reliable fix.
| Component | Typical Parasitic Draw (mA) | Notes |
|---|
| Factory Alarm System (Healthy) | 20 - 50 mA | This is the baseline; should not cause issues with a good battery. |
| Faulty Alarm Sensor/Module | 100 - 500 mA | A malfunction can significantly increase draw, leading to quick drain. |
| Glove Box Light Stuck On | 5 - 10 mA | A small but common issue if the switch is faulty. |
| Infotainment System (Memory Retention) | 10 - 30 mA | Normal for preserving settings. |
| Aftermarket GPS Tracker | 25 - 75 mA | Often a major source of drain if not installed properly. |
| Interior Light Door Switch Issue | 50 - 150 mA | If a door isn't fully closed or the switch is broken. |
| OEM Keyless Entry Module | 15 - 35 mA | Standard for remote functionality. |
