Tow Doctor™ Vehicle Wire Harness Test Unit 

• Tests all tow VEHICLE functions: ground, auxiliary power, brake, direction, and backup.
• Designed so that one person can make sure a vehicle wiring harness has been installed properly and all functions are working
• Heavy duty, 20 ft extension cord is included
• Saves time and the cost of a second person at the rear of the vehicle
• Adapts to 4-Wire Flat, 6-Pole Round, or 7 RV Blade. 7-Way pin type available