Where in the code is it referencing pin 15 (that may or may not be a stupid question :/)?
A1 is an alias. On a 328-based Arduino, the alias has a value of 15.
It looks like whatever you have connected to analog pin 1 is not providing a voltage that the Arduino can read, so it appears that the pin is floating. You do have whatever is connected to analog pin 1 also connected to ground, right?