This is the primary cause of trailer-light problems. Symptoms include flickering, fast-blinking, dimness, intermittent operation (often when a trailer ball is used for a ground), and complete failure.
Peterson’s Genesis lighting system and repairable J560 connector target two persistent fleet problems: LED light failures and ...
According to Phillips Industries, the December edition of its monthly Qwik Tech Tips newsletter outlines “in clear language” how best to troubleshoot trailer lights when they are not working properly.