From the description, it seems like it might be the wiring between the receiver and the left speaker. You'll want to make sure that there aren't any strands touching across the terminals at either the receiver end or the speaker end. If any strands are touching, they can cause a short - and that would cause the receiver to go into protection mode and start clicking.
It might be the receiver or speaker, but I'd start with the wiring. People on here run into that exact thing from time to time.