The charger is indicating a problem with either the battery pack or the charger itself. A blinking red light on the charger means PROBLEM PACK OR CHARGER.
- Unplug the charger from the outlet.
- Remove the battery pack from the charger cavity.
- Inspect the charger and battery terminals for foreign material. Look for conductive debris like grinding dust, metal chips, steel wool, or aluminum foil.
- Clean any debris away carefully with the charger unplugged and the battery removed.
- Reinsert the battery pack. Replug the charger. If the light is still blinking red, the battery pack or charger is faulty.
If that didn't work, the battery pack is too hot or too cold. The charger has a HOT/COLD DELAY feature. It will not charge until the battery temperature is within the acceptable range. Let the battery sit at room temperature for an hour and try again.
Heads up: Only charge DeWalt 20V Max rechargeable battery packs. Using other types of batteries may cause them to overheat and burst.