Arrived on site to diagnose a no cooling system. New AC system was just added in recently. Upon arrival found thermostat and furnace had power but out door unit did not turn on. Opened electrical compartment found primary control did not halve low voltage. Inspected low voltage wires on condenser. Found wire nut lose and not secured and cut low voltage. Resecured wire nut low voltage was live again and primary engaged and condenser turned on and was operational and cooling. Advised client of simple fix. Vibration May have made wire nut lose and cause to cut low voltage. System is now operational and cooling. Did not collect Any payment due to it being install warranty. Cycled system. System is operational upon departure.