Help with sewing machine tension problem

[CraftySewingCrochet]

Hello. I have a Singer HD6335M (relatively new to me, got it September last year). I have been using it fine with no problems. Yesterday it was making a noise and thread got bunched up under the fabric. It was sewing a few layers of fabric at the time but it's supposed to be a heavy duty machine so is meant for that. Anyway since then the tension is not right. The bottom thread is showing through the top of the fabric and the top thread is kind of just sitting straight across the top of the fabric. It suggests the tension for the top thread is too tight I believe.

I have tried rethreading (multiple times), I have tried different threads and a different bobbin and a new needle. I am using the same thread for top and bobbin each time. I have tried adjusting the tension dial too but it does not seem to help. I can feel reducing the tension dial does have an effect on the tension of the thread if I gently pull on it but no improvement in the result on the fabric.

Does anyone have any ideas about what else I can try or what the problem could be?

I have messaged Singer but await a reply and really want to get back to my sewing! Thank you.

Probably nothing to do with your issue, but I once took my machine to a repairer for a similar issue and it turned out I’d put the needle in backwards. My new machine has a shaped hole so that can’t happen though, so maybe it’s only old machines where that’s possible.

Thanks. I'm pretty sure I have it round the right way. There is a flat part where it slots into the machine which I have at the back but I will double check that is right.

Is it the right size needle for the fabric?

The original issue sounds like birdsnesting, which is where the thread unhooks itself from the loopy bit which goes up and down.

I would try a total rethread and sew on something easy like doubled over cotton and see if you can get that to work and then try altering the tension for the thicker fabric.

Are you using the right kind of needle for the type of fabric? That makes a big difference - check in the manual.

Make sure your presser foot is up before rethreading the machines. Also clean out underneath your bobbin.
If none of those, there could be a fault and your timing has gone. It will need a service.