What to Check When the Light on a Trailer are Not Working
Question:
What are possible reasons for lights not working?
asked by: Mark S
Expert Reply:
Lights not working on a trailer can be caused by quite a few different things. The first thing to check is all your grounds. A bad ground can cause any number of things to happen and is always a good place to start.
From there, you will need to check the towing fuses to make sure they are still in good condition. You will need to confirm which these are in your owner's manual. If one or more have blown, it will definitely cause the issue you are having. If all the towing fuses look good, you will need to check the plug on the back of the vehicle.
Using a tester, like the Circuit Tester # PTW2993, you will need to test the pins on the plug. If you have a 7 Way connection, the 2 o'clock position will be your 12-volt power, the 3 o'clock position will be the right turn signal and right brake signal, the 5 o'clock position will be your brake controller output, the 7 o'clock position will be your ground, the 9 o'clock position will be the left turn signal and left brake, the 11 o'clock position will be the tail light and running lights, and the center position will be the auxiliary circuit. If one or more of these are not working, you will need to then check the wires on the back of the plug to see if there is power going into the ports. If there is power at the back of the plug, you will need to replace the 7 Way with something like the Hopkins # HM40975. This would be a great replacement as long as the vehicle came pre-wired with the 7 Way plug. If it did not come pre-wired or if there was no power at the back of the plug, you will need to trace the wires back from the 7 Way connection as there is most likely either a break in one or more of the wires or the ground has become corroded or not secure. If this is the case, you can simply repair the wire and get back to towing, or you could rewire everything and use the Hopkins # HM40975-11998 at the end of the vehicle to give you a clean look.
If the lights still are not working, you probably have a break in one or more wires on the trailer and will need to follow them to find said break. That being said, you should always start this directly behind the plug that connects to the vehicle. These do go bad over time and are easily replaced. The Hopkins # HM20086 has built in test lights to make things easier if this ever happens again.
Products Referenced in This Question
Hopkins 7-Way RV Style Connector w/ Molded Cable and LED Test Lights - Trailer End - 6' Long
- Trailer Wiring
- Trailer Connectors
- Trailer End Connector
- 6 - 10 Feet Long
- Plug and Lead
- 7 Round - Blade
- Hopkins
more information >
7- and 4-Pole Trailer Connector Socket w/ Mounting Bracket - Vehicle End
- Custom Fit Vehicle Wiring
- Trailer Hitch Wiring
- No Converter
- Custom Fit
- 7 Round - Blade
- 4 Flat
- Hopkins
more information >
7-Pole and 4-Pole Trailer Connector Sockets w/ Mounting Bracket and Wiring - Vehicle End
- Custom Fit Vehicle Wiring
- Trailer Hitch Wiring
- No Converter
- Custom Fit
- 4 Flat
- 7 Round - Blade
- Hopkins
more information >
Product Page this Question was Asked From
T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector
- Custom Fit Vehicle Wiring
- Trailer Hitch Wiring
- Converter
- Custom Fit
- 4 Flat
- Tekonsha
more information >
Featured Help Information
Instructions
Miscellaneous Media
Continue Researching
- Shop: Dexter Hydraulic Brake Line with Fittings - 25" Long
- Shop: Trailer Wiring
- Shop: Hopkins 7-Way RV Style Connector w/ Molded Cable and LED Test Lights - Trailer End - 6' Long
- Video: Titan Trailer Brakes T0980100 Review
- Shop: Kodiak Disc Brakes - 8" Hub/Rotor - 5 on 4-1/2 - Dacromet - 3,500 lbs - E-Z Lube
- Shop: Trailer Hitch
- Video: Review of Demco 12 Flexible Trailer Brake Hose - DM02032
- Video: Titan Brake Line Tee with Mounting Bracket Installation
- Video: Review of Demco Brake Actuator - Surge Brake Actuator - DM62VR
- Video: Demco Electric Lockout Hydraulic Brake Actuator Installation
- Video: Titan Trailer Brakes T0778500 Review
- Video: Demco Hydraulic Brake Line Kit for Trailers Review
- Q&A: Flexible Brake Line For Fold Away Coupler Hinge Kit
- Shop: Dexter Bracket for Flexible Brake Line Tubing
- Shop: Replacement Brake Line Retainer Clip for Demco Brake Line Kits - Qty 1
- Shop: Demco Hydraulic Brake Actuator w/ Electric Lockout - Disc - Zinc - 2" Ball - 7,000 lbs
- Shop: Kodiak Hydraulic Brake Hose - 3/16" Male Fittings w/ Stainless Flares - 1/8" ID - 18'
- Article: Trailer Wiring Diagrams
- Q&A: Wiring Configuration of Mighty Cord 7-Way Plug A10-7W10
- Q&A: How To Wire a Trailer Connector With Uncommon Wire Colors
- Q&A: 7-Way Molded Trailer Connector with 10 Feet Length
- Q&A: How To Plug 1997 Lance Truck Camper Into 7-way Connector On 2016 Ford F-250
- Q&A: What is the Difference Between a 4-Way and 7-Way Trailer Connector
- Article: 7 Common Questions Everyone Has About Trailer Tires
- Q&A: How To Wire the Curt Push-To-Test Trailer Breakaway Kit C52042
- Search Results: wiring pigtail
- Search Results: pigtail
- Search Results: 47435
- Search Results: 4 way trailer harness
- Search Results: 56083