There no effect of characterMotor on Firstperson (Player)

Hi guys i made a script which is that that we go below 10 Y axis then character motor value forward sideways gravity fall speed etc change to 2; so when i go below 10 y axis nothing happens to player speed. I checked character motor values that these are changing or not by minimizing the play mode These were changing but i dont know why theres no effect to player speed Forward , sideways or fall speed. every time i use character motor function this happens . iAm using 5.56b unity version