Performed service diagnostic. Diagnostic found that the condensate drain line was clogged. Water had back up and tripped the safety switch. Options for repair were presented to the customer and they chose to have a drain service completed today and sign up for our semiannual maintenance plan. The first of two visits will be completed this Fall/Winter. Drain line was cleared and flow tested with water. Drain line was treated. System was function checked and was running at the time of departure.