How to Test Trailer Connector to Determine Function Assignment on Each Pin

Updated 09/18/2017 | Published 09/16/2017

Question:

My husband is trying to hook up lights to his tow car 2010 Toyota Corolla, manual behind this truck and is having gobs of problems. The wiring he is using is exactly what he uses when he tows behind an International truck and it works just fine then. So....why is it different? He simply cannot figure it out and we HAVE to, otherwise, we have to reject this load and ask our dispatcher to take him off of it. We are transporters He is using a 7-Way Round Pin Trailer Connector. I am doing the typing for him as he doesnt type. Help would be appreciated.

asked by: Delores

Expert Reply:

The 6-way and 7-way trailer connector formats can be configured in more than one way. Please refer to the linked article on trailer wiring that shows the different ways 6-way, and 7-way connectors can have their functions assigned.

On a 6-way round-pin setup the center pin is usually assigned to carry 12V power, but it can also be used for a brake signal for a trailer or tow dolly. On a 7-way blade-pin connector there are also multiple ways those circuits can be assigned.

The best way to know what signal each contact on the truck's connector is intended to deliver is to test with a circuit tester like # PTW2993. Use is shown in the linked video. Since wire colors and function assignments can vary testing is the best way to know for sure what function each pin on the connector is intended to do. Most likely the issue is due only to the two trucks having different wiring configurations.

expert reply by: Adam R