My QC3 has stopped working in one ear and I'm pretty sure it's a dislodged wiring near the 2.5 plug. I can remove the headphone pads but can't see any screws to get to the wiring to check. So there's a trick. Everything on the net is about replacing the pads.
We do not recommend in taking a part your headphones. If you would like to look into service, please reach out to your local Bose product support team. You can reach out to your local support team via clicking this link and selecting your region, this will redirect you to our website. Please scroll to the bottom of the website and there you will find a 'Contact Us' tab, this will provide you with all the relevant contact information for your country.