A:Answer If you are referring to the green light on the charger, it does blink on and off during the charging cycle. Once the batteries are fully charged, it shows a steady green. If there is a defective battery that cannot be charged, the light will show (or blink?) red. As for the charger going on and off, I have not experienced that with mine (this is the second one I have owned - no problem with the first, I just needed two!). It does have a fan noise though, but I think that is on constantly when batteries are being charged.