I have just installed a magnetometer onto my arducopter and enabled the magnetometer, and set the declination.  But when i test it in the Mission planner, it always moves the heading to point North.  I rotate the arducopter, heading changes to reflect rotation, but then drifts back to north in about 1/2 seconds.  I then tried another magnetometer from a friend and it works perfectly so I am guessing I have a bad Magnetometer?

Do I contact the store or is there something I can do to fix it myself?