Is ACC Constant Power?
3 Answers
ACC is not constant power. The ACC position can supply power to some electrical components in the car without starting the engine. Here is an introduction to the four positions on the car ignition switch: 1. LOCK position: The lock position. If the key is turned to the LOCK position, the entire vehicle will lose power, and the steering wheel will be locked. At this time, the key can also be removed. 2. ACC position: The ACC position is the accessory power position. When the key is turned to this position, the accessory circuit will be activated. 3. ON position: The ON position is the power-on position. When the key is in this position, all vehicle circuits will be activated, and the system will begin necessary preparations and self-checks. During normal driving, the key remains in this position. 4. START position: The START position is the engine start position. When the key is turned to this position, the starter circuit is activated, causing the engine to run and start.
As a car enthusiast, I often discuss this topic with friends. ACC is the ignition switch position in a car, representing accessory power. It only supplies electricity when the key is turned to ACC or ON, such as powering the radio. Constant power refers to circuits that remain energized continuously, like the car's clock or anti-theft system, which keep working even after the key is removed. Therefore, ACC is not constant power, and this distinction is crucial. If you accidentally confuse them—for example, connecting a dashcam to ACC when it should be on constant power—it will continue running after the car is turned off, quickly draining the battery. I recommend using a multimeter to check voltage when working on your car to ensure correct wiring and avoid short circuits or electrical failures. Regular inspections can prevent such issues.
Having driven for decades, I once mistakenly thought ACC was constant power when installing a charger, and the car stopped working after turning off the power. Consulting a professional, I learned that ACC only supplies power to the cigarette lighter or horn in specific key positions, while constant power, like the alarm system, stays live 24/7. ACC is definitely not constant power. This lesson taught me to always check the fuse box labels first to distinguish between the two when inspecting circuits now. Similar situations, like modifying audio systems or power banks, can waste battery life if done wrong. It's advised to use a circuit tester for safety first. Experience shows that even small oversights can lead to big troubles.
