Arrived in La Grange for AC Maintenance, Upon our arrival we spoke with the customer about their concerns with the system shutting down. Performing our diagnostics we found that the system is a negative pressure system and was not equipped with a vent after the ptrap as well as the water removal system was backed up. We spoke with the customer about our concerns, went over repair options and maintenance program. Customer approved HF3A and the maintenance today. We cleared the water removal system, installed a vent pipe and checked the system performance. Found everything operating properly at this time.