Arrived at residence for a tripped 16 SEER Lennox unit that had tripped its breaker. Customer reset breaker prior to this technician's arrival and was consistently operating during the diagnostic. Checked temps and amperage on the circuit. Found the L2 side of the AC breaker excessively hot due to a loose wire lug causingthe breaker to trip on high temp. Retightened all wiring leading back to the unit. After testing, found no excessive heat loads that could likely trip the breaker again. System to cool to customer preference. Service warranty.