Upon arrival talked to customer determined what unit was having the problem. Performed diagnostic found system with popped low-voltage fuse. replaced fuse it immediately popped indicating system has a low-voltage short will need low-voltage short detection. The low-voltage short detection found problem with low voltage thermostat wiring. during inspection found low-voltage wiring for low pressure switch almost rubbed through creating another low-voltage short. repaired both low-voltage wiring locations supported wire with zip ties away from copper tubing to prevent electrical short from happening again. replaced low-voltage fuse tested system operation found no other problems at this time.