Lexus RX300 battery drainage issue persists despite new alternator and battery installation on Lexus RX300

Some Lexus RX300 owners report experiencing persistent battery drainage issues even after installing a new alternator and battery. These owners have identified several potential causes, including faulty wiring, particularly to components like the back dome light, which can lead to significant battery drain. Additionally, some have noted the presence of parasitic battery drain, causing the battery to lose charge when the vehicle is not in use. Electrical system malfunctions, such as issues with the vehicle's computer or faulty switches like the door or ignition switch, may also contribute to the problem. In some cases, owners find that the root cause of the battery drainage remains undetected despite multiple inspections. Furthermore, a high current drain from various systems, including locks and monitoring systems, can exacerbate the issue. Lastly, a malfunctioning alarm system has been reported by some owners as a continuous power draw, further impacting battery life. It is crucial for owners to conduct a thorough inspection of the electrical system and components to identify and resolve the underlying causes of battery drainage in their Lexus RX300.