Help! My Air Compressor Won't Charge the Battery - Just Hums

Hey guys, I got this small 1 gallon air compressor from Harbor Freight last year, and now the battery won't charge. When I plug it in, it just hums and the little light doesn't turn green. I'm on a budget, so I don't want to buy a new one. Any ideas?

Felix, first thing, check if the battery is actually bad. Take it out and test it with a multimeter. If it's not holding a charge, it might just need a new battery. They're not too expensive. Also, make sure the charger isn't the issue. Sometimes the connections get dirty. Clean the terminals with some sandpaper or a wire brush.

Yeah, what Paul said. But also, I've seen them hum when the compressor's check valve is stuck. That would keep the tank pressure from rising, so the motor never kicks in fully. You can usually clear that by bleeding the tank and tapping the valve lightly with a wrench. But since you mentioned battery, I'm thinking it's electric start? If it's an electric start, the battery might just be a trickle charger for the electronics. Check the wiring for any loose connections or corrosion.

Thanks guys, I'll try cleaning the terminals and checking the check valve. The multimeter I got shows the battery has 12 volts, so maybe it's the charger. I'm gonna borrow my buddy's charger to test. But if that doesn't work, I'll look into the check valve. Appreciate the help!