Abstract: An alarm system for an AC assembly having an exterior located condenser supplied by a pressurized refrigerant system flowing between interior and exterior locations of a structure. A power source supplies an alarm panel at interior locations of the structure. A normally closed fluid pressure switch is electrically coupled between the power source and alarm panel and is maintained in an open and fluid communicating position upon detecting a continuous inlet fluid pressure. The pressure switch recloses upon sensing a decrease or loss of pressure, at which point a relay communicating closes to complete an electrical circuit between the power source and alarm panel. An alarm output in communication with the alarm panel responds to the closing of the relay to issue an alarm condition.