Troubleshooting Trailer with Bad Running Lights
Question:
I have working torn signals, brake lights, and flashers. But when I turn on my head lights. The trailer lights dont light up
asked by: Chuck W
Expert Reply:
There are a few things that could be going on. The first thing you want to do is isolate whether the issue is on the vehicle or the trailer. Start by using a circuit tester, like part # PTW2993, to test each function on the trailer connector at the back of your vehicle. If the running light circuit isn't working here, then the problem is on the vehicle. In which case start by checking the connector for any debris or damage as well as any trailer related fuses. Also, make sure the ground wire on the trailer harness is connected to a good, clean, bare metal surface. If all of these are good, you need to inspect the wiring starting at the connector and moving towards the front of the vehicle. Look for any pinched or damaged wires. Also, inspect the connector where the harness plugs in to the vehicle's wiring.
If the vehicle connetor all checked out then the issue is on the trailer. Here you basically want to check the same things; inspect the connector for debris or damage, make sure the ground is good, and follow the wiring from the connector to the lights looking for damage.
If you still can't solve the problem let me know what you found while troubleshooting and we'll go from there.
Product Page this Question was Asked From
Continue Researching
- Article: Trailer Wiring Diagrams
- Q&A: Trailer Running Lights Do Not Work but Brake Lights and Turn Signals Do Work
- Article: Brake Controller 7- and 4-Way Installation Kit (ETBC7)
- Article: Brake Controller Installation: Starting from Scratch
- Article: Testing Trailer Brake Magnets for Proper Function
- Article: Troubleshooting 4 and 5-Way Wiring Installations
- Article: Troubleshooting Brake Controller Installations
- Q&A: How to Make an Adapter to Go from Semi Truck 7-Way Round to RV Style 7-Way Blade on Trailer
- Q&A: Will The Curt Dinghy Wire Harness # C96JR Interfere With Activation Of A Blue Ox Patriot
- Q&A: Trailer Turn Signals Both Blink when Just Left Turn Signal is Activated
- Q&A: Trailer Lights Left Side Turn Signal and Brake Lights Not Working
- Q&A: Troubleshooting No Running Lights on Trailer but Turn Signals and Brake Lights Work
- Q&A: Troubleshooting Lack of 12V Power at 7-Way Trailer Connector on 2019 Ford F-150
- Article: Trailer Lighting Requirements