I just repaired a pair of in ear headphones that were working in the left ear but not the right, I though I would though up some pictures to help others.
Quick rule when repairing anything, look at the problem and try to do the Simplest things first. with that in mind.
Step 1. plug headphones into a number of music devices and see if the headphones work.
Step 2. try and work out at what point up the headphones stop working. In terms of how far up the headphone cable is still currently working, In my case, right ear was not working but volume up and down buttons still work so I knew the little PCB in there was still ok. but the wires from the top of the PCB to the Right earpiece would need to be looked at.
Step 3. Take it Apart!
I carefully pried the volume controller apart with a very thin knife carefully not to cut the pcd or damage the plastic tabs.
PCB close up for people who are interested.
Step 4. Determine problem.
Mine had a white wire that had come free from the R- contact
Step 5.
I re-soldered the wire to the joint, and put a little hot glue on top to stop the wires being tugged in and coming off again.
Step 6.
Test before putting back together (mine worked)
Step 7.
I had to put some heat shrink over the volume butted plastice at either ed to keep it together.
Step 8.
Another common problem with these type of headphones is the wires at the ear peace break
These can be fixed the same way.
Wiring diagrams can be found on google which can be useful if you need to replace a headphone jack!
good luck with your repairs! if you have tips/problems please put them in the comments!