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Trailer Hitch Installed and Lights Go Haywire


We’ve all heard  horror stories about how add-on equipment can cause unexpected and hard to resolve problems elsewhere in the electrical system. Here’s a great case study where that exact problem happened and how the root cause of the problem was found and resolved. In this case, John from California was trying to resolve a 2017 Jeep Cherokee Trailhawk with issues with rear light operation after a trailer hitch and trailer light wiring were installed.

In this case study, John walks through his diagnostic process in detailed fashion, complete with scope captures, showing how he verified the source of the problem prior to replacing any parts. As one commenter stated in relation to vehicle sensitivity to add-on parts: “…[These] circuits are not designed to handle such an operation. Simply installing a wrong resistance bulb will freak these “smart lighting” systems out… The old days of simple electrical circuits have long past. We are in the age of very sensitive electronic circuits.”

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