The pilot was on a return, cross country flight to his home airport in instrument meteorological conditions. The pilot reported that he first performed a non-precision approach into the airport, where he reported that the landing gear extended normally. After performing a missed approach, the pilot retracted the landing gear and he then performed a precision approach in the opposite direction. The pilot reported that he put the landing gear switch in the down position, but that the landing gear did not extend. The pilot elected to continue the approach without troubleshooting, extending the gear manually, or referring to the emergency checklist. The pilot subsequently landed the airplane on the runway with the landing gear retracted, which resulted in substantial damage to the fuselage. After the accident, the pilot performed an operational check and troubleshooting of the landing gear without authorization. The pilot reported that the landing gear again failed to extend, but would retract during his testing. The pilot also reported that the manual landing gear extension system operated normally. During the testing, the pilot said he found an “open circuit of the gear relay due to moisture or foreign debris.” After troubleshooting, the pilot reported that the landing gear started to operate normally. After the pilot had performed the unauthorized troubleshooting, a Federal Aviation Administration inspector examined the landing gear system, and performed a functional test, during which he found that it operated normally.