For the last six months the compressor has worked as advertised. Today I tried to use the 120V AC function and the 'on' button got stuck in the 'on' position so it started as soon as I plugged it in. It's annoying that it broke after so little use. But it still works! I am updating this review to 5 stars as the company has replaced this unit with a brand new one! They really stand behind their product and I've used a "broken" compressor with a stuck "on" button with no problems. For customers who have a defective device, I recommend contacting the company at the email address provided in the user manual. They will respond promptly and send you a new block with no further questions. Good value for money!