Welding help needed

So the last time that I used this welder, a few weeks ago, to weld a winch onto my trailer, it started acting weird half way through the job. It started acting as if it was running out of sheilding gas. Yes, it is 120v. The argon tank has plenty in it, when i pull the trigger I can see the needle on the output gas guage move, and I can hear the gas coming out the end of the gun.