I was just given a 401A , it runs great except for the upper tension discs no matter what it is set at when the foot is down the thread will not go through the discs. Does any one have any suggestion on how to fix it as it is going to a group home for disabled adults when I get it fixed.
First open up the nose cover on the machine. As you raise and lower the presser foot, do you see the thing behind the tension move - that pushes a pin in and out. If it moves it in and out, your best bet is to take the tension apart and put it back together. If you can follow a pattern you can follow the instructions to do this. It isn't really all that hard. Here are some instructions. http://www.tfsr.org/publications/tec...achine_manual/ - look for instructions that are like your machine. Your owner's manual may have that same info. Here is a 401 repair manual - I think you have to scroll 125 or so pages to find it though. http://parts.singerco.com/IPsvcManuals/306W25.pdf Make sure all the parts to the tension, including the center pin is there. Oh and when you lift the foot and it does not move that thing in and out it is probably something in the foot lift area of the machine. I would have to look that over real good to figure out how to fix that. That lever does more than just lift the foot on any sewing machine - they just work different from one machine to another. Keep us all posted how it goes.
To add just a bit to what Miriam posted, if and when you remove the tension unit from the machine, remove the set screw that holds it in. Push a piece of thin wire through the hole to make sure there is no debris in the hole.
Our machine had constant tension problems like yours is showing. It would not hold adjustments and when the presser foot was lowered it would get real tight.
When I took it apart I noticed some shiny metal in the hole the set screw should protrude from. It was aluminum shavings from when the set screw hole was tapped. As the screw was tightened to hold the tension unit this debris would compress and the tension would be pushed out by the pin and lever.
Once I cleaned all this debris out and reset the tension it has worked perfectly.