Hi,
I assume you are using a UNO or Nano Arduino controller.
Try using another analog input rather than A4 or A5, they are also connected to the I2C /wire().
When you use your test code, you do not have the wire() function operating.
In your full code you do use wire(), and A4 and A5 are then used as I2C comms pins.
This link will help explain;
Tom... 
