M12 Fuel 1/2" impact won't charge - light flashing red/green

Hey guys, my Milwaukee M12 Fuel 1/2" impact driver stopped charging yesterday. The charger light flashes red and green when I put the battery in. Tried two different batteries and both do the same thing on the charger. Batteries are about 2 years old. Any ideas before I toss the charger?

Classic M12 charger issue. That flashing pattern usually means the charger detected a faulty battery or connection. First, clean the contacts on both charger and batteries with a pencil eraser or rubbing alcohol. Also, check the charging port for any debris. If that doesn't work, try a different outlet or let the battery cool down completely before charging again. Sometimes they get too warm and won't charge.

Had the same thing with my M18. Turned out one of the pins in the charger was bent slightly. I carefully straightened it with a tiny screwdriver and it worked fine after. Another thing: make sure the battery is seated all the way down - sometimes they don't click fully.

If cleaning and pin checks don't work, it's likely a dead battery cell. M12 batteries have a BMS that can lock them out. You can try jump-starting it with a known good battery if you have one (look up the method online) but honestly, replacement batteries aren't that expensive. If both batteries act the same, it's probably the charger. Milwaukee has a 5-year warranty on chargers - check your date code.

Thanks for the tips! I cleaned the contacts and straightened one pin that looked a bit off. Now it's charging normally. Saved me buying a new charger. You guys are legends!