Left side of my headphone is not working

That often happens because of a contact on the headphone wiring, The only way to fix it is by taking apart headphones, testing the wire, and checking the headphones solder joints on the speakers and on jack connector, that usually are responsible for this kind of problems.

Sounds like a dirty plug or a broken wire in the cord. Yes, it can be fixed.

Halpe me cdma haier c1000 re sat code

The left side is more problematic, since the circuitry and most of the wiring is there. It is a job to get into, and this is only for people who are comfortable with a multimeter and either very strong glasses or a loupe.

You have to carefully saw the plastic all the way around the seam - this seam is about 1/4" from the ear-pads. Use as thin a cutting blade as you can find. Saw until you hit metal, all the way around, then pry the end off.

Remove the white plastic foam inserts, and you will see three very small torcs screws with T8 heads. Once loose, you can pull the silver part off.

From there you can do some continuity checking. In my case, one of the headphone wires was touching another component on the circuit board, and bending it away from that was enough to restore sound to the left side.

Putting it back together: well, it will not be a pretty as it was. You have to line up the on-off slide with the switch, but then the silver side goes on quite easily. Do not over-tighten the tiny T8 screws.

You can use gel-superglue to put the ring/ear cushions back, but do not add glue until the ring is almost in place. You may find that you have to do some gluing of the ear pads afterwards. I suppose some black electrical tape might cover the scar you'll have from sawing, but if you find the problem, that might be an acceptable price. It was for me.
Best of luck