The 6 built-in stitches (such as blind stitch, darning stitch, etc.) are not working, they only just do the basic zig zag stitch. Also the cams for decorative stitching do not work either. These are all on an Elna Air Electronic SU. Any ideas please

Suspect the machine has seized due to lack of regular cleaning and oiling.

Elna Carina Electronic SU Duplex Review

Wheel on right side that controls the needle up and down is very tight...

You should probably take it for service.

...

the machine needs to be checked to see if the gear or cam for the decorative stiches is damaged or broken

it's very possible that a cam or gear has worn down or broken
inside the machine and also if the sewing machine is computerized
then there could be a problem there, having the machine checked
would tell you for sure.

You have the machine set for blind hem stitching. Change the stitch selector to stretch stitch, which is a single, in line stitching zig zag stitch.

Cheers,
Embroidery Services
San Diego, CA

here is a link to great info on sewing.about.com which explains this technique with images, http://sewing.about.com/od/techniques/ss/machineblindsti.htm

In brief, you need to fold the fabric to be hemmed into a Z shape with the wrong side hem edge at the bottom of the Z.

The Blind stitch is either three straight stitches then a wide zig zag which swings to the left and catches a little bit of the folded edge, or three small zig zags, then one wide zig zag to the left to catch one stitch into the folded edge. The zig zag style has a little more stretch in it so works good on jerseys and knits.
You need to use the blind hemming foot which helps you to line up the folded edge and keep it at a constant distance from the needle. It will look like this.
Turn the little silver screw to move the white plastic guide left or right until you've got just a smidgen of fabric being stitched by the left wide stitch. Always do a practice sample first to get the stitching and guide set right. On most machines you can vary the width of the big zig by adjusting the stitch width dial a little.

You need to adjust the blind hemming foot guide so that the needle is just catching a tiny amount of your folded fabric because this is the stitch which shows on the right side of the fabric when you unfold the Z. So forget trying to hem satin or expensive fabrics this way, a hand sewn stitch will give a much better finish.

Blind hemming works best on a hem which is continuously straight on the same grain line, its not great for a curved hem. So if you've got a tiered skirt or the frill on a bed valance, it is fine as the fabric edge to be hemmed will be a continuous straight length. You can use it on a slightly curved hem for jerseys as the fabric has more give, and patterns will help to disguise the stitching too.

I hope that this helps you to sew your blind hem, 4 thumbs up if so.

No the stitch is only on certain machines like the lady sitchb studio locate din Albany NY.
Thank you,
Marie

I have the same model, have you turned the first knob on left, the stitch selector, to the stitch you want? Then turn the middle knob, the stitch width to "4". Use the colour guide marks shown in the little picture on left of the knobs so you are dialing up the right settings. So for the zig zag, elastic blind hem, scallop, overcasting and multi-stretch stiches, 1-6 on the diagram you'll be setting the left knob to 1, 2, 3, 4, 5 and 6 respectively and the stitch width and length knobs to "green", you can vary the length and width to suit what you want.

Then for the cams, you need to set everything zero, turn stitch selector to 7, the cam setting. then turn the width to orange again (3-4) and the stitch lenth selector to the orange setting, right around the knob. This engages the "Elnagraph" the device under the flap on top of the machine to read the discs. Basically the green stitches the needle is swinging from side to side while the feed dogs move the fabric forward, making your zig zags, blind hems etc.
But when you engage the Elna graph, the machine matches stiches by moving the fabric "forward and backwards at certain times, while the needle does its thing from side to side. This is what makes elastic or stretchy type stitches because you are putting "stretch" into the seam by sewing forwards and backwards.

Please note: always turn your stitch width and length back to Zero BEFORE you make any changes to the left knob and select a new stitch as this saves on wear and tear to the moving parts in these wonderful machines.

I do hope this assists you and I haven't just told you stuff you already knew!

a all purpose foot or a zig zag foot will do both straight stitch & zig zag

Darning would normally be done with the triple stretch stich, the one that is a zig-zag broken up into three stitches right and then three stitches left. See-through Zig-Zag foot. Zig-Zag set at it's widest. Feed set to about 1/16-1/8 inch (1.5-3mm) and darn by sewing forward a bit, adjust fabric, and then backward by pressing and holding the reverse button. Continue back and forth until you've created a darned box. For extra strength, turn fabric 90 degrees and repeat over same area.