I always use WD40 to spray into the 7-pin socket and move it all around to clean the contacts... I think we all have a can of WD40 and some DUCT TAPE on board... Even some bailing wire haha...
Never leave home without them haha...
Since you have replaced the 7-way connector it must be a ground or something not right with the leads feeding the rear hookup.
My truck has the DUAL 7-way and four way trailer connector as a unit with spring door that is used for locking into the trailer plug...
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Roy Ken
