It should give you a pretty decent vibration. Remember, you can set the intensity make sure this portion is done for your watch not accidentally for your phone settings will be under the watch where app and type of vibration; this can often make a difference in how strong it feels. Also, make sure you wear the watch snugly so you can feel the vibration motor at its full capabilities.
If you're pretty sure its defective, I would use the diagnostic tool under the members app and do a warranty claim. You can also do a manufacturer's reset and see if it helps at all
