Singer sewing machine 6215c trouble w/stitching - top looks fine, underside all loops of thread

the looping on the bottom usually is a tension problem, the top & bottom tension are unequal usually fixed by adjusting the top tension.
some people that I've talked with have had success with changing to a different size needle ( depends what type of thread is being used).
when the machine is threaded the foot needs to be up ( this releases tension on the thread), when the foot is lowered it the tension is set on the thread. if the material being sewed is too thick it raises the foot too high & releases tension on the thread ( the material has to be really thick to do this).
if there a piece of thread or lint in or around the tensioner or bobbin area it could cause trouble.
other wise if you've tried everything you can think of, take it back th the store & have them try it & tell you what is wrong.

also this machine has bad reviews (i'll provide a link so you can read them), people having the same problems as you are. the newer singers just don't seem to be the same quality tha the older ones were.
all bad reviews
http://www.amazon.com/Singer-5400-60-stitch-Sewing-Machine/product-reviews/B007ZG9DTQ/ref=cm_cr_pr_btm_link_1?ie=UTF8&showViewpoints=0&sortBy=byRankDescending
mixed reviews
http://reviews.walmart.com/1336/20573406/singer-5400-sew-mate-60-stitch-sewing-machine-5400-reviews/reviews.htm

What kind of thread are you using. The most often problem today is that the thread is too thick for the size of needle. Try using a Metallica size 90 or a top stitching needle size 90
if the thread is a cotton type or a quilting thread it is often to thick to travel easily through the eye of a needle quickly to form a good stitch.

count the beeps and refer to the owners manaul as for troublshooting tips

Firstly check the tension on your bobbin case is sufficient or if the thread is actually into the spring fully, this is most likely cause of bottom thread loose stitching. You can test bobbin case tension adjustment using the "Dangle" test, here is a link to some good images to help.
http://www.sewusa.com/Sewing_Machine_Repair/Thread_Tension_Settings.htm

If you look closely and there is actually looping on the underside then is is the top thread coming to the underside and not being tensioned back up; so top thread is not under tension enough or at all.

Set top tension to 4-5, then recheck the threading up and and always thread with the presser foot raised as this opens up the tension device so the thread can seat in fully. Once you've threaded to just before the needle thread guide, lower the presser foot and pull the thread downwards, it should be very firm if its under tension.

Tension devices can get gunked up or fail with use so if you can't get it to feel firm, it will need a technican to investigate further.

check to see if your needle is bent
check your tension
if you need a manual go to diplodocs.com
in the center on the page select brand-
your is there under singer
then product look up model number
manuals are pdf & free

Raise the presser foot before threading the machine.

What looks like a problem with the bobbin thread is usually due to the machine being threaded with the foot down.

Foot up - tension control opens; foot down - tension control closes.

When the tension control is closed, the thread cannot enter as it should and then cannot be controlled to form a proper stitch with the bobbin thread.

The Singer Sewing Co website has many graphics that are the same for all sewing machines - you can check there with regards to winding, inserting the bobbin into the case/shuttle and bringing up the bobbin thread.

You may have threaded the machine with the presser foot down. This closes the tension control and the thread cannot properly enter during the threading process.

Re-thread with the presser foot up.

Test the stitching.

Hi Lou! This sounds like a tension problem--the tension on the top thread is too loose. Try using different color threads on the top and bobbin, then carefully rethread everything. Stitch a couple of inches and check the underside. If the top stitches look fine and the bottom ones are loose and loopy, and with the pressure foot down, tighten the tension. Move the knob or dial (whichever you have) just a little bit. Sew a couple of inches more, and recheck. Continue to sew and recheck, gradually tightening the tension, until you see little if any bobbin thread on the top or top thread on the underside of the fabric.

Let me know if this helps, ok?


Robbie

This is a tension adjustment problem. It's good to use two different colors of thread, like you did. From your description, the top thread (needle thread) tension needs to be tighter. As you tighten the tension of the top thread, you'll see that the top thread pulls the bobbin thread up into the fabric so it's no longer laying loose on the bottom of the fabric.

You'll need to have the pressure foot down when you tighten the tension. Tighten it a little, sew a practice seam, check to see what the stitch looks like. Tighten it a little more, sew, check, etc etc--until both top and bottom look the same--you shouldn't see much (if any) of the bobbin thread color on top of the fabric or the top thread color on the underside.

Let me know how this works for you, ok?


Robbie

Try oiling the hook if you haven't recently.
Check you needle plate and hook for damage, they may need to be buffed or sanded smooth.
Check your upper tension discs for lint and double check your upper thread path (proper threading).
There are other things like hook timing, needle clearance or broken check spring that may be wrong but you need a technician for those things.
best of luck!