It can happen too when its in your car and the headlights are off. This is because the dimmer option is still active in your car when the headlights are off, its just that the dimmer is set to 100% (you can adjust the dimmer with your headlights on or off, there are two dimmer settings.but you can only play around with one of them while you are in the house if you force dc mode). Until mine warms up, I can turn the headlights on and off 10 times and get 10 different brightness levels without ever changing the setting. It just does whatever the heck it wants...