Left ear doesn't play any sound.

Hi @enesesen

It could be a fractured wire in the cable, a loose connection to the earphone left speaker or a faulty speaker.

Try flexing the cable near to the plug end and the headphone end and check if you can make the audio in the left speaker come and go. If it is a cable problem, this may help to narrow it down to where it is

If you have a DMM (digital multimeter) you could test the wiring from the cable plug right up to where it terminates in the headphones and test the speaker as well from that point.

Here's a video that may help.

If the cable is fractured near to the plug end and needs to be replaced, it is easier to cut the cable back to where it tests OK (I realize that this shortens the cable) and connect it to a new 3.5mm TRS plug (tip, ring sleeve). If it is fractured near to the headphone end, again you could cut it back and reterminate the cable in the headphones. Take pictures before you disconnect the wires in the headphones so you know where to reterminate them again. You will need soldering tools and skills to do the repair.

By convention, with a 3 ring TRS plug, the left speaker is connected to the tip, the right speaker is connected to the ring and the common return is connected to the sleeve. see image below