Troubleshooting Trailer Wiring When Running Lights Do Not Work

Question

Question:

Ive got a flat 5 connector to a boat trailer. Everything works, right left signals, brakes, emergency but no running lights. All the functions above work with the truck lights on also, but no running lights. Ive checked and bridged across all the trailer ground connections and all connections on the vehicle side are showing voltage including brown. Just cant use the trailer at night. I purchased a new 24inch 5 flat extention from you last week and it is installed. old one was shot. Needed. . . but did not help.

asked by: Mike M

0

Expert Reply:

It sounds like there is a ground wire issue on your trailer. Since you said you checked the vehicle harness, and it checks out we can rule that out as the issue.

You will want to use a circuit tester like part # PTW2993 and check the wires coming out of the trailer connector when plugged into the vehicle. Make sure the pin for the ground on the trailer connector is not corroded or bent. Check the lights and make sure the ground wires are securely fastened to a clean bare metal surface, and that none are broken.

expert reply by: Jeffrey L

0

Answer 1

If you are not getting power on the running light circuit at the connector on the truck then none of the running lights should be working on the trailer. Trailer's in the US use one circuit for running lights, one circuit for left turn/brake…

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Answer 2

Everything works okay until you activate the running lights and draw maximum amperage through the system. This is the classic symptom of an insufficient ground connection. Find the main grounding point on the trailer by tracing the white wire from…

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Answer 3

This sounds like a ground issue. Ground problems normally show up when there is more draw on a system such as when you have the running lights on and then use another function like a turn signal or brake light. Make sure that the vehicle side and…

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Answer 4

Since all of your trailer lights operate properly with the exception of one of the running lights, this tells us that the vehicle wiring harness is probably working properly. I would first carefully check the bad light's ground and power wires to…

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Answer 5

You will first want to check the fuses on your tow vehicle. Some vehicles could have fuses for operating the turn signals and brake lights of a towing package. You will want to check if they are installed and working properly. The next thing is to…

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Answer 6

LED lights only require a very small amount of amperage/voltage to partially light up. What you are experiencing is a little bleed through on your running light circuit. So somehow there is a small short between an active circuit on your trailer…

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Answer 7

First thing to check is for corrosion on the trailer wiring connectors on the running light circuit. Nearly everytime a single circuit stops working on trailer wiring it's due to corrosion in the connectors preventing the connection being made.…

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Answer 8

I absolutely agree with you that what you are experiencing is a ground issue; moving it to a frame with a clean metal surface is going to resolve the issue in nearly every case. If it was a short you would still be having issues with lights not…

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Answer 9

My suspicion is that you have a poor ground connection somewhere on your trailer. The fact that everything works fine until the running lights are turned on is the dead giveaway. When the tail lights are turned on, the trailer lighting is drawing…

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Answer 10

First thing you should do at this point is test the 7-way of the wiring harness with a circuit tester part #PTW2993 for voltage on all of the right pins when the taillight signals are being applied. Just like in the video I attached. If the voltage…

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Answer 11

The difference between the Class II and Class III hitches has to do with their Gross Trailer Weight (GTW), their Tongue Weight (TW), and their Hitch Receiver Size. Class II trailer hitch receivers have a 1-1/4 inch receiver and can be rated up to…

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Answer 12

A 4-Way trailer connector has the basic lighting functions only; running lights, left turn signal and brake lights, right turn signal and brake lights, and ground. A 7-Way has these functions and a 12 volt circuit, a circuit for electric trailer…

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Troubleshooting Trailer Wiring When Running Lights Do Not Work

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