I just bought a bike with a shimano exage 300 lx group. The left shifter (trigger) will not click into place. It will move the front drailer but the shifter just doesn't click. The upshift trigger will move the drailer but the down shift trigger will move but doesn't move the drailer. I tried adjusting the barrel and the adjustment screws on the drailer but no luck. I'm not sure if it needs adjusting, cleaning or replacing. I thought I would go to the pros for some help.

Thanks
Mutt