Trailer Marker Lights are Not Working But All Other Lights Work

Question

Question:

Trailer marker lights are out. The 4 ways and the turn signals do. I have a 7 way plug. I checked the truck fuses and they seem to be fine. I would appreciate any ideas you may have.

asked by: Jeff G

0

Expert Reply:

To determine where the problem is first disconnect the trailer from the tow vehicle. Use a circuit tester such as # PTW2993 or a meter if you have one to test the vehicle side trailer connector while the head lights are on. If there is power on the pin in the 11 o'clock position, then the issue is on the trailer. If there is no power during this test the issue is on the tow vehicle. Besides fuses some vehicle tow package wiring also use relays. The various fuse panel lids under the hood, and in the cab on some vehicles, will list the fuse and relay functions so you can find any relays related to the tow package wiring.

If there is power when testing, then the issue is on the trailer side. It could be something simple just as a corroded trailer connector. Make sure the trailer side (and the vehicle side while you're at it) is clean and free of corrosion inside, where the wires attach, and outside on the pins.

If you are still having problems, inspect the wiring from the connector back and fix any pinched or damaged wires.

It could also be a ground issue. the lights should be grounded to clean and corrosion free bare metal surfaces. If there is anything between a light ground and the metal trailer frame or if the trailer has an aluminum frame, tilt bed, or folding tongue, any of these things can interrupt the ground. Running jumper wires from the light grounds to the main trailer connector ground can help.

Another possibility is that if the trailer has a lot of running lights the combined power draw may be too much for the tow package wiring to handle. To test this, you can disconnect some of the lights that use the running light circuit and if the others start working then that was indeed the issue. Switching to LED lights would solve that problem.

expert reply by: Michael H

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Answer 1

It could be a tow package fuse on the vehicle. Use the owners manual to find the locations of fuses/relays related to the tow package wiring to check them and replace as needed. If the issue is not a fuse or relay then you can test the vehicle side…

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Answer 2

It sounds like you do not have the side marker lights properly grounded. If the lights have a separate ground wire to attach to the trailer frame it will need to be connected to a suitable point on the trailer frame. The closer to the light the…

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Answer 3

The 4-way on your trailer is what's known as a wishbone connector like part #A35W42B. Two of the wires are the running light circuit which is a little easier to install since you can run one down each side of the trailer. This way you don't…

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Answer 4

Below is the general process for bleeding an electric over hydraulic brake actuator like #K71-650. Fill reservoir with NEW brake fluid. Never re-use brake fluid that has been salvaged or removed from another system. Remove the key from the breakaway…

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Answer 5

I have added a photo detailing the wiring connections for the Pollack Heavy-Duty, 7-Pole, Round Pin conncetor, #PK11700, see link. This is a SAE J560 compliant connector. The wiring diagram for the vehicle side connector, #PK11720, is pictured also.…

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Answer 6

On your 1999 Ranger boat trailer with tandem axles, I recommend the Replacement Shackle Link with Bolts for Dexter Trailer Suspension Kits #018-026-05. If instead you want to piece together your system, I recommend using the Locknut - 9/16"…

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Answer 7

The only 1 leaf, 1-3/4 inch wide leaf spring we offer is #e46SR. This spring sounds like it might be a fit for your trailer. It is a single leaf double eye spring that measures 25-1/4 inches long from center of eye to center of eye. This spring is…

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Answer 8

This is a common issue on certain Nissan vehicles. You are likely missing a relay for the trailer running lights in the tow package wiring on the Frontier or the relay could have gone bad. Use the owners manual to find the relay and fuse locations…

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Answer 9

The problem you are having is a classic ground issue. If the ground wire to the trailer frame or the tail light grounds are not connected securely to clean, rust and paint free surfaces then when the headlights are turned the extra amperage draw for…

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Answer 10

Henschen has been out of business for about 12 years, so I wasn't able to find much information about your axles online. From what I saw in the forums, they used a standard spindle for a 3.5K axle, so it should use a L44649 outer and a L68149…

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Answer 11

On a 7 pin round which is the common connection on a semi trailer, the clearance/marker lights are at the 10 o clock position when you look at the trailer wiring connection. When looking at the connector on the back of the truck, that will put the…

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Answer 12

The LMX red grease like the Lubrimatic LMX part #L11390 that you referenced is what I recommend. This is perfectly compatible with the Lithium based grease your hubs have in them now and is considered to be the most heavy duty option available. Using…

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Trailer Marker Lights are Not Working But All Other Lights Work

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