P28R pilot reported main landing indicating not down and locked. After landing determined that the gear down lock switch was malfunctioning.

Narrative

On the Day 0; I was operating a Piper Arrow / P28R on a private flight from ZZZZ1 to ZZZZ2. During final approach; after lowering the landing gear; the left gear did not indicate as down and locked at approximately XA:20. I then aborted the approach; checked the bulbs; which were all working; and recycled the gear once; without success. However; the gear retracted normally.Since ZZZZ2 is a remote airport with no infrastructure; I decided to divert to ZZZZ. This was the best airport we could reach at that time; considering our endurance; the approaching sunrise; and also the availability of fire brigade services; as well as the runway length and width. I then rechecked everything in the vicinity of ZZZZ: the bulbs; the circuit breakers; and went through the Emergency Landing Gear Extension Procedure in the POH (including the amplified procedures and the system section). Unfortunately; this did not resolve the issue.I then performed three fly-bys and received a visual inspection from an aircraft that happened to be in the area; flying nearby; using its camera. The gear appeared to be locked. As a precautionary measure; I however decided to prepare the aircraft and the two passengers for a landing with a partially extended landing gear. One fire truck was standing by. The landing; which took place at around XB:50; was uneventful; and we filled out an incident report provided by ZZZZ AFIS.We then inspected the gear again; which was mechanically locked; and found a loose contact in the terminal wire of the left-hand landing gear down lock switch.