welcome to the forum ECaro03!

Your code is not to far but you must know the followings...

1. PIC16F684 use several oscillator config. Default setting is suppose to be 4MHZ. but it's safe to use this line at the top of your code.

OSCCON=%01100000 'define internal oscillator to 4MHZ


2. you must turn off a/d converter to read digital signal from PORTA by using

ANSEL=0 'turn off a/d


3. you also must turn off analog comparator by using

CMCON0=%00000111


now i sugest the following modify code.

Code:
OSCCON=%01100000 'define internal oscillator to 4MHZ
ANSEL=0 'turn off a/d
CMCON0=%00000111

trisa = %11111111
trisc = %00000000

portc = %00000000

left     VAR     PORTA.0 'define left as PORTA.0 status


loop:
     if left then
          portc.0 = 1
          pause 2500
          portc.0 = 0
     endif

     goto loop
what about now?