How do I know if the tension is correct?

There is no default setting on the machine at this time. If the problem is on one needle, you can start by pulling the thread and feeling its tension. It shouldn’t be too tight or too loose. Check the needles that are functioning properly and try to mimic their tension. As you pull, you should be able to feel when problem needle has reached the same tension as the needles that are working well. Once you believe you have acquired a good standard tension, try an “I” tension test. During the “I” test, you should follow the one-third rule. Make sure you have one-third of bobbin thread in the middle and one-third of top thread on both sides. Generally, if you have fairly even columns, your tension should be correct.