Chosen Solution
I got a second hand iPhone SE and the headphone jack wasn’t working - there was hissing and other noises. Wobbling the headphone plug sometimes helped a little, but then it quickly went back to hissing again. I tried several headphones - same result. Then I decided to change the whole audio-jack/charging port assembly. Luckily I have another iPhone SE with a working headphone jack. I replaced the unit, but the sound problem didn’t go away - same hissing and crackling. I then put back the original part, and now even wobbling the plug doesn’t do anything - it’s now just noises and hissing. I wonder - if changing the headphones jack unit doesn’t help, what else could be wrong?
The next step would be checking the connector on the logic board. If it is only the headphones that aren’t working and you have ruled out parts there is not much else it can be.
