Lonestar Guy
Well-known member
Was getting weirded out. But first... 1) I worked for 40 years on complex biomedical instruments, so I'm somewhat technically competent. (Still learning RV stuff) 2) I know my right from my left. 
OK, pull-behind trailer lights have worked fine, except for when there was a break in the left side wiring at the light, (cause unknown but maybe chewed through by rodent). That one I fixed and all was fine for long trip to SD.
During recent more local trip, got indication the left tail light had an issue (I think it was.) Finally getting around to testing and it, starting with the truck plug (2015 F150 with tow package), and it 'appears' the truck wiring is reversed, left and right blinkers, at least. What?!?! Plugged trailer in and magically it works now.... properly... left and right lights and signals. Not sure what 'fixed' it or what was wrong to start with. Obviously, I checked the snugness of connection and reconnected and looked checked bulb, etc. Anyway...
So... back to the truck receptacle. Right pin is active when left turn signal is on and vice verse. Finally dawned on me... the truck connection is mounted inverted compared to virtually every plug pinout diagram that comes up in Google! The key is on the bottom of the receptacle. Doh! : I guess it's been too long since I worked. I've lost my edge! The plug's key is usually the starting point for this kind of debugging but I missed that indicator straight away. Oh well.
Just thought I'd share. I hope it's not a waste of everyone's time reading this. If we shouldn't post anecdotal stories, let me know.
OK, pull-behind trailer lights have worked fine, except for when there was a break in the left side wiring at the light, (cause unknown but maybe chewed through by rodent). That one I fixed and all was fine for long trip to SD.
During recent more local trip, got indication the left tail light had an issue (I think it was.) Finally getting around to testing and it, starting with the truck plug (2015 F150 with tow package), and it 'appears' the truck wiring is reversed, left and right blinkers, at least. What?!?! Plugged trailer in and magically it works now.... properly... left and right lights and signals. Not sure what 'fixed' it or what was wrong to start with. Obviously, I checked the snugness of connection and reconnected and looked checked bulb, etc. Anyway...
So... back to the truck receptacle. Right pin is active when left turn signal is on and vice verse. Finally dawned on me... the truck connection is mounted inverted compared to virtually every plug pinout diagram that comes up in Google! The key is on the bottom of the receptacle. Doh! :
I guess it's been too long since I worked. I've lost my edge! The plug's key is usually the starting point for this kind of debugging but I missed that indicator straight away. Oh well.Just thought I'd share. I hope it's not a waste of everyone's time reading this. If we shouldn't post anecdotal stories, let me know.
