Shimano tourney 7 speed shifter for rear not working My bike's shifter for lowering the rear gears is not working. It just slide all the way and "click", "click" sound comes but gear does't shift to lower ones. Its currently stuck at the 7th gear and won't shift. The cable also appears to be a little loose. What should I do? Please help.
The cable could have broken, leaving the derailleur sitting on the smallest cog on the upper limit.  I had this a few weeks ago, the cable had broken within the shifter so was not immediately visible.

If when shifting you feel little or no resistance when trying to change to a lower gear this will be a good indicator that this is the problem.