Cadence sensor dead after changing battery

Put in a new battery and now won't work at all. Speed sensor is fine after battery change. Checked with a different battery, nothing. Did the flip battery and left open just in case this would work. The white card fell out - does it have to put back in a specific position?
  • This thread worked for me - after spending :45 minutes trying to figure it out.  The metal piece in the removable cap (light silver color) has to be lined-up correctly so that the long contactor "finger" lines-up with the + terminal contactor in the body of the sensor.  In my case the metal insert popped out of the removable cap with the battery - when I re-inserted it it was no longer correctly aligned.  Poor design - the metal pickup in the removable cap should be fixed to the cap so that It can't become misaligned.  Once I corrected alignment the sensor fired right up.

  • does the led flash green upon battery replacement in the sensor?  If not it's not powered - check the alignment of the metal piece in the removable battery cap - it has a long rectangular piece which rises to the top of the cap (when turned upside down) and this is what makes contact between the + battery terminal of the sensor and the battery holder (metal piece inside the cap).  The metal piece in the cap can become rotated out of alignment with the pickups in the body of the sensor - when this happens the +  side no longer makes contact and the sensor won't be powered.  Took me :45 minutes and finding this thread to fix it...  

  • does the led flash green upon battery replacement in the sensor?  If not it's not powered - check the alignment of the metal piece in the removable battery cap - it has a long rectangular piece which rises to the top of the cap (when turned upside down) and this is what makes contact between the + battery terminal of the sensor and the battery holder (metal piece inside the cap).  The metal piece in the cap can become rotated out of alignment with the pickups in the body of the sensor - when this happens the +  side no longer makes contact and the sensor won't be powered.  Took me :45 minutes and finding this thread to fix it...

  • More follow-up for future reference.  The LED is located a few mm above the "N" in Garmin.  There is no discernible external indication of the location as the LED is actually UNDER a thin spot in the black casing (weatherproofing, I assume.)  I was beginning to doubt there really was an LED until it magically flashed!  

    In the cavity in the body of the sensor are two brass contacts.  The first, very obvious, is the negative (-) contact, a twinned brass arm that sticks out to almost the middle of the cavity and touches the negative (-) side of the battery when inserted.  The second is a very short (~3mm) contact, about where the "lock" icon is on the case, that presses against a silver contact lip on the battery door when it's closed and locked and provides the positive (+) connection.  In my case, that 2nd short tab appears to have been too low to press against the silver lip, so I pried it up a bit.  It actually took several tries to get it high enough to touch the silver bar.  Just for good measure, I also pried out the three silver vertical contacts on the opposite side of the battery door to ensure the positive rim of the battery had a good contact.