EE repairing the A/C on a Cat 789C rock truck when he attempted to ascend the equipment ladder he felt a pull in his left shoulder, no medical attention was given & EE finished his shift. *EE worked until 8/20/14 when he began missing due to a non-work related illness. Upon release from his illness he was unable to RTW. It was determined to be related to the incident of 7/8/14.