You have power but is it enougft? See if you have a breaker going bad in you box. It's like a weak breaker and a electric clothes dryer in your house. The lights will come on and the fan will run but not the power to make any heat.
I have a Daytona mig I bought in 1985 still welds like a dream. I keep it covered by a plastic bag when not in use. It's very important to keep dust out of a welder.
