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.

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.

Tesla and NHTSA have confirmed that a recall has been issued on some Model Y vehicles over a trailer brake light failure. The good news is that the fix is an over-the-air software update. NHTSA ...