Dead battery!

We recently went on vacation to Hawaii. One morning, just before sunrise, we drove our rental car down the coast to a harbor for a snorkeling trip. I decided to be safe and use the headlights.

When the boat got back to the harbor after the snorkeling trip, our rental car's battery was dead. I had left the headlights on. I hadn't done that since I drove an old Volkswagen Bug years ago. I tried to figure out what happened. After some experimentation, I discovered that if the headlight control was in the ON position when one turned off the engine and got out of the car, then the headlights remained on and there was no warning sound. Just like my old Volkswagen!

At home I have never had a dead battery by leaving the headlights on in our two vehicles. In our car, if  the headlights are left in the ON position with the engine off, a warning sound occurs when the driver's door is opened. In our SUV, if the headlights are left in the ON position with the engine off,  then the headlights turn off automatically when the driver's door is opened.

After more experimentation, much to my wife's annoyance, I discovered the AUTO mode on the headlight control in the rental car (see photo) is apparently designed to prevent one from leaving the headlights on when the engine is off. In AUTO mode, the headlights automatically go on when the engine is turned on AND you either release the brake OR you shift the car out of park.

Design Suggestions

Here are some design suggestions that would have prevented a dead battery:

• A warning signal that the headlights were on after the engine was off and the driver door was opened.
• An AUTO mode that would automatically turn on the headlights when the engine was started rather than waiting until the car was switched out of park or the brakes released. Had this been the case, I would have left the headlights in AUTO mode and the headlights would have turned off automatically when the engine was turned off.
• An ON/OFF switch would be sufficient. Having both an ON and AUTO mode is too complicated. I think our SUV works well. If the headlight switch is set to ON, the headlights turn off automatically when the engine is turned off and the driver door is opened. The headlights turn back on automatically when the engine is started.

NOTE: If you want to keep the headlights on with the SUV engine turned off and the door opened, you flip the headlight switch OFF and then ON again. This solution for keeping the headlights on while the engine is off takes advantage of people's tendency to press a button multiple times if it doesn't work the first time.