Help with Steering

I'm attempting to build an autonomous line follower and having problems getting my car object to follow the white line. I'm using wheel colliders on the hind wheels but for some reason the car object wont turn. The problem might be with the Turn functions. I'm wondering if just setting a steer angle turns right and its negative turns left.

Sample Code :

void TurnRight()
{ if (sensor1.s1_detect && sensor2.s2_detect && !sensor3.s3_detect)
{
SteerAngle = 6;
FL.steerAngle = SteerAngle;
FR.steerAngle = SteerAngle;

     }  
 }  

void TurnLeft()
{
if (!sensor1.s1_detect && sensor2.s2_detect && sensor3.s3_detect)
{
SteerAngle = 6;
FL.steerAngle = SteerAngle;
FR.steerAngle = SteerAngle;

     }  
 }