Singer Sewing Machine 401A Troubleshooting (Fix & Repair)

Even Singer sewing machines break down or have problems with dirt and oil. As good as the sewing machine may be not one of them are immune to the common problems or a rise in the dirt levels. A little elbow grease, a checklist, and time will help keep the 401A running.

Three things you should have for any sewing machine model including the 401A. #1. a maintenance/cleaning schedule; #2. an oiling schedule; & #3. a checklist of potential trouble spots to check before calling the repairman.

To learn more about fixing and repairing a Singer 401A sewing machine just continue to read our article. It gives you the common problems and some solutions to help your machine keep working at optimum levels.

Singer 401A Not Working


This is why you need a checklist. If you can cover those easy-to-spot problems before going to a repairman and suffering some embarrassment over forgetting to plug the machine in, the better off you are.

A checklist will help you spot simple problems like the presser foot has not been lowered, the bobbin winder has not been put back into the sew position, and other simple fixes. You may have threaded the machine wrong or forgot to turn the machine on before stepping on the foot control.

Also, the machine may be dirty in key spots preventing the sewing machine from operating like it should or you forgot to oil the machine. All of these issues can prevent the machine from starting.

Even the thread not going through the eye of the needle correctly may stop the machine from sewing. Then from there, you can check the wiring in the foot pedal, the needle position and if it is inserted correctly, and so on.

How to Fix a Singer 401A

This is a vintage machine and it may have been one of the last to have all metal parts. The key to fixing this sewing machine model is to make sure you get the right parts for it.

If the tension knob is stuck, you can loosen it up with a little oil but be careful when using non Singer lubricants. They can mess up a sewing machine due to the differences in chemical formulas.

Often, a good cleaning and good oiling are all that is needed in order to get the machine up and running. Unless a part is actually broken most fixes are quite easy to do. Since the machine is about 70 years old, you won’t have to worry about voiding the warranty if you work on it yourself. Check the needle to make sure it is not broken or bent, etc., and check the bobbin area also as those are common suspects when the 401A does not work right.

Singer 401A Not Turning On

This can be an electrical problem. The first place you need to check is the power switch to make sure you turned it on and after that, look at the power cord. If it is not plugged in, you have found the source of your problem.

Plug the cord back in and if the machine still doesn't turn on, look to the wiring in the power cord and the foot pedal. There may be a loose connection or a wire is frayed and shorting out on you.

If your model has a knee lever then check the wiring on that device. When you are done with the wiring and everything is in perfect working order, check to see if any of the parts are stuck. This situation can prevent the machine from working.

There might be a problem with the motor and since the motor is also 70 years old, it may not have the strength to continue working. A replacement will be in the cards. The fix is easy and you should get a good repairman to handle it anyways. They will make sure the machine is up and running by the time they are done.

Singer 401A Stitch Selector Stuck


The first place to look is the camstack and see if it is frozen with dry grease. This is one of the more common sources when this situation arises. The grease can dry up on you or get more solid making it hard to move the lever.

Some grease issues cannot be solved by using WD-40 or other solvents. You may have to turn to rubbing alcohol to get the job done. Also, a small flat head screwdriver may be needed to scrape off the hardened grease.

This task will take some time to do so make sure you block out enough time to get the task done. A little heat from a hairdryer may be in order as well. Grease will loosen when the heat is applied.

Every situation may be different so you may need to be prepared to find a new part if the old one is not going to work right even after you do the above maintenance on it.

Singer 401A Tension Problems

The first place to look will be the bobbin. Make sure that not only is it inserted corrected, that it is the right one as well. If those areas and items are okay, then move on to the next common source, dirt, grime, and lubrication. Make sure everything is clean and up-to-date oiling and maintenance wise.

Once those areas are cleared, look at your thread. If you are using the wrong kind, like quilting or embroidery thread you may have a tension problem. To return to the bobbin for a moment, avoid using plastic ones in the 401A. They damage too easily.

Also, if you oil the edge of the bobbin case, you may stop your tension problems as well. One person did find that if she replaced her worn-out metal bobbin with a plastic one, she solved her tension problems. But the plastic one will wear out faster and probably a metal one should be used instead.

The quality of metal bobbins may be lacking these days and you have to be careful of the ones you put inside the 401A.

Singer 401A Thread Keeps Breaking

The first place to start is to see if the thread was threaded correctly or not. You may have to re-thread the machine several times before you find the problem. It may not be the threading that is the cause.

It could be that the upper tension is set to the wrong level and is way too tight for the machine and fabric. Another cause would be that there is something in the way of the thread keeping it from moving as it should.

Check your thread path and the tension dial to make sure these are not the cause of the thread breaking. Also, check the type of thread you are using. Rayon is a weak option and can break on you very easily. Switch threads if this is the case.

Other areas to check would be the bobbin, the needle, and also see if there are any sharp burrs in the way of the thread. Those sharp burrs are hard to see and find so you may have to be hands-on there and fell the thread path with your fingers.

How do You Adjust the Tension On a Singer 401A?


There should be a thread tension dial on the 401A that does the job. All you have to do is turn the knob to a higher or lower number until you get the right amount of tension on the thread.

For the bobbin tension, you will have to open up the bobbin case and get a small screwdriver and turn the screw in the right direction. To tighten you need to turn that screw clockwise and to loosen the tension, you need to turn it counterclockwise.

To get the right tension, it may take a little practice, and make sure to use a scrap piece of fabric first. That way you won’t ruin the good fabric you are working on. Once you get the tension set right, you should be good to go and the machine should sew as you want it to.

Also, make sure you are using the right thread. The wrong thread may break on you even if you have the tension right. The strength of the wrong thread is not always that great.

Singer 401A Needle Position

This is one of the more important aspects of sewing with the 401A. The needle must be selected according to the thread used and the fabric being sewed. It s eye must be large enough for the thread to pass through and the point strong enough to go through the fabric correctly.

To insert the needle correctly, the flat side must be facing the back of the machine while the long groove is facing you. Of course, Singer says that your best results will be coming if you use a Singer-made needle.

Also, make sure to raise the needle bar all the way up before you try to insert the needle. Watch out for bent or broken needles. They can slip by you if you are not paying attention.

Bent or broken needles will cause you a lot of common sewing machine problems when you are not careful. Plus, a dull needle is not good to have in your machine. Make sure to change the needle regularly so that you are always using the sharpest needle possible.

Singer 401A Serial Number Location

One of the problems with contacting Singer for the serial number of your 401A. If you can’t find it, they will just give you all the serial numbers they issued for a certain letter combination. You may have a hard time finding the serial number for your machine in that response.

However, to find the one on your model, you may have to lift the machine as it is on the bottom near the needle plate. There should be 2 letters and 6 numbers and the letters are NA, NB & NC, and 401As, and other Singer models all received serial numbers with those letters.

Also, the Singer corporation will release all serial numbers for a given pair of letters. For example, if the NA series started in 1951 and made 1,000,000 in that series over the next 7 years, you will receive a list of one million serial numbers dating to 1951.

But the company may have made only 10,000 machines in 1951, 100,000 in 1952, and so on. Do you see the problem? You may be able to find the serial number easily but dating your machine is a little more complicated.

Downloading a Singer 401A Instruction Manual


Getting a hold of a Singer 401A manual is less complicated than finding the date your machine was made. There are lots of good websites to go to in order to find a copy you can download.

Our go-to manual site did not let us down this time. You can find one here. It is new to us so we are not sure how it works. On top of those two choices, you can try Singer itself. Their manual web page is found at this link and it should not be too hard to navigate to what you want.

Then you can try this location. It has more than enough manuals for all different types of Singer sewing machines and they are supposed to be free. There are something like 15 pages at least filled with manuals.

If those sites do not work for you, then a good internet search should bring you more results. Take your time as not all of these sites are free and you may end up paying for some in British Pounds if you are not careful.

Singer 401A Motor

The image we looked at for this model sewing machine showed that it used the Singer sewing motor. It is a shaft-driven motor that inserts into the bottom of your machine and sits there until you need to clean it.

It is possible to clean the brushes on this motor with a Q tip so you can help keep it in good running order with a little time investment. Plus, it looks to be a workhorse of a motor with some lasting a very long time under perfect conditions.

Also, you should be able to find replacement motors and parts at eBay. Just keep checking if you do not see any for sale the first time. Parts are not hard to come by and sometimes the Singer website has parts for sale to make it even easier for you to find a replacement if it does burn out on you.

What Size Bobbin for Singer 401A

The size of bobbin you want will be class 66. It does come in plastic form and it may work well for you. But the thing about plastic is that it can wear down a lot quicker than metal can.

The cost is relatively cheap with one store selling them for $4.99 for 5 or a dollar each. You may be able to find cheaper ones at different locations.

Also, if you can get a hold of class 66 metal bobbins buy them. They seem to be a dying breed. Singer does sell class 66 bobbins in different pack sizes and fairly cheaper than the one we quoted. You can find them at this link.

Go to a repair shop or other store dealing with sewing machine accessories to see if you can get metal bobbins for your 401A.

How to Oil a Singer 401A


This is not a difficult task to perform. But in the 70 years since this model was made, Singer has changed their oil formula. You may have to search around to get the old formula in order to effectively lubricate your 401A.

Singer usually recommends that you only use Singer oil when doing this task but you may find compatible brands at a lower price. It is very difficult to describe all the oil points the 401A has.

Some Final Words

The 401A has been around for along time. It has proven its worth by its longevity and being able to sew long after its production date. If you want to troubleshoot other Singer sewing machines, we suggest you visit our web page covering that topic. Just click Troubleshooting a Singer Sewing Machine to get to it.

Singer sewing machines are fairly simple machines for basic repairs and fixes. For more difficult repairs we suggest you go to a qualified repairman and let them get the job done for you.

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