Troubleshooting Low Output Voltage on Hopkins Trailer Taillight Converter Box
Updated 05/22/2025 | Published 08/02/2017
Question:
Hello Experts, Application: Trailer hookup from International school bus. Qty 4 ea model: 310-0041-560 Rev. c09-10 All four converters outputs are 5vDC or less to trailer. Voltage in to converter is 12vDC. What could cause the low output?
asked by: Mike M
Expert Reply:
It's possible the converter has an internal short and is damaged. Or it could be possible that you have a weak ground for the converter. Most likely though the box has shorted out. They are designed to fail as a way to prevent a short in trailer wiring from making it back up to the vehicle wiring so that is what is happening.
You'd want to track down the short on the trailer wiring and fix it before replacing the converter.
Product Page this Question was Asked From
Hopkins Tail Light Converter with 4-Way Flat Trailer Connector
- Custom Fit Vehicle Wiring
- Trailer Hitch Wiring
- Vehicle End Connector
- Converter
- Universal Fit
- 4 Flat
- Plug and Lead
- Splice-In
- Hopkins
more information >
Featured Help Information
Instructions
Miscellaneous Media
Continue Researching
- Shop: Trailer Wiring
- Shop: T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector
- Video: Trailer Wiring Harness Installation - 2002 Chevrolet Express Van
- Shop: Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector
- Q&A: Troubleshooting Hopkins Tail Light Wiring Converter
- Video: Set up: T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector on a 2014 Nissan Murano
- Video: Feature Breakdown: T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector-118362
- Q&A: Can a Taillight Converter Module Go Bad After Working Properly for Months
- Shop: T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector
- Shop: T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector
- Video: A Closer Look at the LED Combination Trailer Tail Lights
- Shop: LED Combination Trailer Tail Lights - Submersible - Driver and Passenger Side - 25' Wire Harness
- Shop: Peterson Light Kit for Trailers Under 80" Wide - 20' Harness - Driver and Passenger
- Shop: Hopkins Tail Light Converter with 4-Way Flat Trailer Connector
- Search Results: trailer wiring
- Q&A: What is the Difference Between a Class II and a Class III Hitch?
- Shop: Trailer Hitch
- Article: Brake Controller 7- and 4-Way Installation Kit (ETBC7)
- Article: Trailer Wiring Diagrams
- Shop: Brake Controller
- Video: How to Choose a Trailer Brake Controller
- Q&A: What is the Difference Between a 4-Way and 7-Way Trailer Connector
- Search Results: trailer hitch
- Article: Wiring Trailer Lights with a 7-Way Plug (It's Easier Than You Think)
- Video: Feature Breakdown: Universal Installation Kit for Trailer Brake Controller
- Q&A: What Is An OEM Prep Package And How Do I Know If I Have It
- Search Results: trailer brake controller
- Shop: Suspension Enhancement
- Q&A: Lug Nut Torque Chart for Trailer Wheels
- Search Results: trailer lights
on Custom Fit Vehicle Wiring
Dave
5/22/2025
I am having the exact same issue and am pulling my hair out. All of my outputs are 5 - 6V. I just got a new box and it is wired up correctly. Using a keychain tester everything works fine, but plugged into the trailer I get no lights at all. I tested the trailer using a separate 12V battery and everything works fine. The lights are new a year or two ago, and the car is new. All fuses are fine and the cars tail lights work fine, The trailer has a dedicated ground from the harness to the 2 lights.