With the upgrades completed the experiment was renamed Kamiokande-II, and started data taking in 1985. The experiment spent several years fighting the radon problem, and started taking "production data" in 1987. Once 450 days of data had been accumulated the experiment was able to see a clear enhancement in the number of events which pointed away from sun over random directions. The directional information was the smoking gun signature of solar neutrinos, demonstrating directly for the first time that the sun is a source of neutrinos. The experiment continued to take data for many years and eventually found the solar neutrino flux to be about 1/2 that predicted by solar models. This was in conflict with both the solar models and Davis's experiment, which was ongoing at the time and continued to observe only 1/3 of the predicted signal. This conflict between the flux predicted by solar theory and the radiochemical and water Čerenkov detectors became known as the solar neutrino problem.