Why Can't the Car Start After Leaving the Headlights On for 20 Minutes?
2 Answers
The reasons why the car can't start after leaving the headlights on for 20 minutes are as follows: 1. Insufficient Voltage: When the battery voltage is insufficient, the horn and lights may still work, but they cannot power the starter. The battery light will illuminate when the key is in the ON position before starting the engine, indicating low battery voltage. Use a voltmeter to test the battery voltage. If it is below 10V, consider replacing the battery. 2. Poor Fuel Quality: Check the quality of the fuel added to the car to see if it is caused by carbon deposits. If the car has been driven around 20,000 kilometers, focus on inspecting and cleaning the throttle body and checking the ignition switch. Test and inspect the starter, fuel pump, sensors, and other components related to the starting and fuel supply systems. Additionally, after turning on the ignition, wait for 30 seconds to a minute before starting the engine to see if it makes a difference.
After driving for so many years, I've found that this situation mostly indicates the battery is nearing the end of its life. Keeping the headlights on for 20 minutes actually consumes quite a bit of power, especially for older cars where the battery capacity has degraded and its ability to hold a charge has diminished. At this point, starting the engine requires a sudden surge of high current, but the battery has already discharged to a critical level and simply can't power the starter. It's best to check if the battery has been in use for three to four years or more, and whether there's any corrosion or whitening on the terminals. Once, my car had the same issue, and when the roadside assistance technician arrived with a battery tester, it showed only 30% capacity remaining. Replacing the battery immediately solved the problem. To prolong battery life, try to minimize the use of in-car electronics after turning off the engine.
