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In this work, the crack nucleation under fretting and fretting fatigue loading was investigated experimentally on a Ti-6Al-4V alloy. The geometry considered is a cylinder on flat contact in stick slip conditions. A new dual actuator fretting fatigue device was presented and an original interrupted test expertise methodology was proposed. In order to quantify the crack nucleation, the fretting fatigue set-up was equipped with a potential drop technique device. A proper calibration, presented in this paper, allowed a crack nucleation detection threshold of 50 µm with an error threshold of 10% at the maximum. Three parallel studies have been carried out: fretting loading tests (optical expertise), fretting fatigue test for a lifetime of 100 000 (optical expertise) and fretting fatigue interrupted tests (potential drop technique).These tests have shown that the addition of a fatigue load can provide a fall of 45% of the tangential threshold of crack nucleation compared to simple fretting loading. It has been identified that the crack nucleation is influenced by the fretting and the fatigue forces in two ways: increasing the fatigue load leads to a decrease of the tangential force nucleation threshold whereas raising the fretting load leads to a decrease of the nucleation and fracture fatigue lifetime. All tests curried out with the potential drop technique system have shown that this technique is very efficient in the case of a fretting fatigue test.