Hi, I am getting really frustrated by a snowmachine trailer. I have a 95 Dodge Ram 1500 with a 7 way plug wired in at the bumper and also in the bed. The trailer is a 4 way so I use an adapter to the truck. I recently re-spliced all the connections on the trailer and the grounds. The reason being that only the left side lights, left running light and 3 middle lights were working. The rest on the right were not. After re doing the wiring, doing a very good job with heat shrink connectors, super 88 tape and doing the grounds with fresh bolts, star washers and cleaning the fresh holes drilled in the frame with emory paper. There are grounds for both tail lights near the back and grounds for both forward side lights near the front. Now, the only lights that work are the two tail lights, none of the others have power to them and the tail lights turn off when I press the brakes! Ive checked the blades on my 7 way with a led light and all the correct ones are sending power. I grounded the white wire on the trailer coming from the 4 way near the tongue. Could it be that the ground is not good on the vehicle? The ground wire that is in the 7 way continues with all the other wires in the plastic housing to where it splits off to the tail lights. I cannot tell where it is grounded to. Help!!
asked by: Ben
Do not despair. I will be happy to help. This does sound like a classic ground issue but there could be some other factors involved as well. So we will start with the easy things to check and work our way from there. Testing the trailer connector on the truck was a good start. The next thing you will want to do is plug in the adapter to the 7-Way and test the pins on it. If they are incorrect, there could be a problem with the adapter.
Next, you can plug in the trailer and test the wires coming out from the back side of the trailer side connector. If you are getting the proper signals and voltage here, you know that the issue is further back on the trailer. If you do not see the right signals and voltage, it could indicate a problem with the main ground on the trailer side and/or vehicle side connectors, a problem with the internal parts of the trailer side connector, or a problem with the tow package wiring on the truck.
The main ground from the trailer connectors should be near the connectors themselves. A long ground can cause problems like this. Make sure all grounds are attached to clean and corrosion free bare metal surfaces. No painted surfaces either but it sounds like you have though of that already.
The trailer or vehicle side connectors could have corrosion build up inside of them and you will need to take them apart to check and to check that all the connections are intact.
It is also possible that if you have a lot of lights on a trailer, it could be too much of a power draw for the trailer wiring system from the truck. You will need to determine how many amps the truck can handle from the trailer. If the lights draw too much power, some of them may not work. Stepping on the brake makes the lights brighter which also means more power draw so that could be why they go out.
Or it could still be a ground at the lights themselves.Many lights ground through the mounting studs unless there is a ground wire on the lights. In either case, make sure that all grounds are attached to clean and corrosion free, not painted bare metal surfaces. If you have a plastic fixture like a license plate holder between a mounting stud and the trailer frame, this can also cause a bad ground.
If some of the lights are incandescent and some are LED this can also cause problems with some of the lights not working or being too dim. This is due to the difference in the amount of power each draws. It would be best to go with all incandescent or all LED.
Even though you did a thorough job of making wire connections, it is possible that there is a break in the wiring that you cannot see. The only way to find it would be to use a circuit tester like # 3808 and test the wires starting from the trailer connector and working your way back. This could take some time so if all else fails maybe leave this for last.
I have included a link to our wiring FAQ for you that may help you to troubleshoot the problem.
expert reply by: Michael H
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