Just bought this used machine, it worked fine in tryouts but after transit the stitch width switch is not working. It automatically goes to the reverse position and will not dial down to any widths.

If the zig zag function on your Elna Carina sewing machine is not working, there could be a few possible causes:

1. Incorrect stitch selector: Make sure you have selected the correct stitch on your machine. Double check that you have selected the zig zag stitch, and not accidentally switched to another stitch.
2. Incorrect stitch width: The stitch width knob on your machine controls the width of the zig zag stitch. Make sure that the stitch width is not set to zero, as this would prevent the zig zag function from working. Adjust the stitch width to the desired size.
3. Tension issues: If the thread tension is too tight or too loose, it can affect the zig zag stitch. Check your thread tension to make sure it is set correctly.
4. Clogged machine: Dust, lint, and debris can accumulate inside your sewing machine and affect its performance. Clean your machine thoroughly, including the bobbin area and the feed dogs.

If none of these solutions work, it may be necessary to have your machine serviced by a professional.

Model and make of machine please, as that may make a big difference to what the problem may be.

Without knowing what machines it is, I can ask, does the hand wheel turn ? Does the needle move at all ?

Check that the throat plate is the correct one for the stitch you're doing and has not been raised. Check you have not set for zig zag stitch ( wider stitch width ). Stitch width too wide may put needle out of position so it can't do down.

Why don't you download the manual which will tell you everything you need to know? get it here. http://sewingonline.co.uk/library/JONES-VX-950.html

have you checked the needle to make sure it's in correctly--flat side of needle goes to the back of the machine

correct needle insertion is mandatory for the proper use in your sewing machine. Raise the needle bar to the highest point, then loosen the needle clamp screw to remove the old needle.
place the new needle in the needle clamp with the flat side of the needle facing the back (or if using a round needle the groove in the needle should be facing away from the shaft.
push the needle all the way up to the stop, or as far as it will go, then tighten the needle clamp screw.

how to decide which needle is correct to sew with, it depends on the fabric & thread being used for the project.
like for example, I've been sewing for over 30 years, I'm sewing a stretchy fabric & regular needles won't work because they skip stitches & will pull the fabric thus damaging the fabric, the needle I have to use is a singer universal ball point needles, & I have no problem with the stitches they come out fine.

Is this the duplex model with the base that fits into a sewing cabinet?

My Elna booklet lists a SP "air electronic" duplex (CL.39), if so, then it would be same stitches as the 38, yellow front panel, 7 built in stitches and automatic knob with blue markings for buttonholing.

Here is the SU manual images for buttonholing, should be exactly the same for the SP.

Instructions are:
use buttonhole foot. turn the 3 dials to buttonhole marked in blue (stitch selection, width and length).
Mark length of buttonhol on the material. Place work under foot with the mark in the middile fo the foot, the start being directly below the needle. sew the first side, raise the needle. Turn stitch width dial to 2, blue. Sew a few stitches for bartack. Raise the needle.
Turn stitch width dial to 3 blue. sew the second side. stop just short of the first side. Raise the needle.
turn the stitch width dial to 4 blue. sew a few stitches for bartack. Raise the needle.
Turn stitch width dial to "fastening off stitch" blue dot. Sew a few stitches, holding back the material by hand. Raise needle, lift pressure foot and remove work, triming off threads.
Open the buttonhole with your seam ripper (put a pin across the end to avoid any nasties).

Sounds like the reverse mechanism has jammed...either with lint or lack of use and oil/lint has frozen the mechanism.
Unplug the machine and remove the base. Clean all the lint with small brush and vacuum.
Try the reverse lever to see where the connecting rods are and identify the collar around the bottom shaft....try to move manually, use a little lubricant where the collar moves on the shaft.
In extreme cases it may take several applications over several days to rectify this, but as this is only 3 years old, should respond quickly

I hope you have not left this machine for a year! (If you haven't used it, feel free to send it to me!) Since the tensions on this machine are automatically set with the automatic thread delivery system, check to see if you have stitch dial set for an overlock or a flatlock stitch (which is what you're getting now).

Have you changed your needle? If you have a dull or bent needle it can cause the machine to not lock the stitches together and the result is a straight stitch on every pattern. Also, check your stitch width selector and make sure that it did not get accidently moved.

I have this same issue with that same machine. Did you ever figure out what was wrong with it??

I had a similar problem a couple of years ago. I finally figured out that I had the straight stitch needle plate (the one with the single hole), rather than the zig zag needle plate (the one with the curved hole). When I changed plates, it worked fine.