iPhone does not vibrate with rocker switch

I recently Refurbished my iphone 3g. I replaced ALL components excluding the LCD & the logic board. Everything works fine, except:

When i use the Silent Rocker Switch it does not vibrate. The visual of the switch turning the phone on silent works, appearing on the screen, but it does not vibrate with the action. I cannot check to see if it would work with a call because the phone is not activated, as i have upgraded to the iphone 4. I was planning on giving the phone to my girlfriend after i fixed it, but she does'nt EVER use the ringer and only keeps her phone on vibrate( can be quite annoying), so this a necessary function for her. Any thoughts or suggestions, or better yet a solution? I have made sure that the motor is not obstructed. Thanks guys