Have you ever asked yourself what is the center connector on a 7 blade plug? The purpose of each blade will vary between a trailer end plug and a car end plug, they will both have a blade for tail/marker, charge, right turn, brake, ground and left turn.

The center connector on a 7 blade plug is for auxiliary in case you want to keep the fridge going while on the road - it’s always nice to arrive to your destination knowing you have a cold drink waiting for you!

Here’s an illustration which may help guide you through the wiring process for a 7 blade trailer harness:

Hope you found this helpful! Feel free to add a comment to this post if you have any questions or advice you’d like to share with others.