Only and always reverse lights

[ncredbear]

Okay fellas, I’m sorta bummed right now and could use some words ofwisdom. It has been a couple of months since I have been able to getout fishing and finally was planning on going tomorrow. Thisafternoon checked and loaded gear and hooked up to truck so would beready to go in morning. In checking lights discovered problem. Withtruck in park and lights connected, first thing I noticed is norunning lights. Then I realized, even with truck in park, truckback-up lights were on. Checked and trailer reverse lights were alsoon. Strange! Unplugged trailer lights, back-up lights on truck wentout. Reconnected lights truck back-up lights on even with trucklights turned off. Checked turned signals and brake lights and workedon truck but not on trailer. However at all times reverse lights ontrailer are on no matter what, so long as trailer plugged into truck,and always lit on truck too. My truck has a round 7-pin and thetrailer has a flat 5-pin so I have an adapter. It is molded with the7-pin on one end and the 5-pin molded on the other. I know what I ammost likely to hear, because it is the BBC default for lightingissues “gotta be the ground” and it may be. I was frustrated andit was dark so I didn’t really check anything out yet but it seemsstrange that whatever it is would cause the truck back-up lights toalways be on as soon as I connect up.

[Wallace]

I’m no expert but if the truck came for the factory wiredwith the hitch and the trailer was factory wired and neither have been tampered with and all other things being equal I would look at the adapter . I’ve had to replace one because of terminal corrosion .
The one I replaced the first time didn’t seem to waterproof and where my factory hitch is my trailer light plug goes underwater all the time.

[Brit P]

I would check your wiring on your truck between your plug and the main wiring harness on your truck. It has to be coming from a power source and there's not a power source on the trailer until you plug it in. That's the only thing I can think of off the top of my head. hope that helps. I hate working on trailer lights!

[Champ 2001]

First thing I would do when having weird electrical problems like yours is to YES check the grounds first. If in doubt about your ground situation, make a temp ground wire and run it from the truck to your trailer. That will eliminate the ground if its not the problem. Next get a meter or test light and check all the connections one at a time on your trucks plug. I just had a similar situation on my truck/boat and I found a couple different things. On my harness in side the swing away tongue, the wires were smashed together, chaffed and insulation worn thru to bare wires. Then after that, I found my ground wire bad. I hope yours is something simple. Let us know what you find.

[billnorman1]

Hate to say it but it sounds like a ground issue. Trailer chassis isn't grounding the lights and the voltage is feeding back into the truck chassis. Try it with a different truck.

[fishnfireman]

Is this a new adapter ?
I ask because some are wired different. The constant 12 volt is not in the same location.

[kry29]

Hate to say it but it sounds like a ground issue. Trailer chassis isn't grounding the lights and the voltage is feeding back into the truck chassis. Try it with a different truck.

+1

[CatFan]

If the backup lights are on when no trailer lights are supposed to be on, it doesn’t sound like a ground issue. Sounds like a problem with the truck. Try another truck on your trailer.

[Joe4d]

Assuming truck , adapter, trailer worked correctly last time.
Also Assuming truck is fine when not hooked up,
corrosion or short issue in the trailers connection. Also examine the cable for a crease, where it looks like it might have been pinched.
You basically have current coming from the running or always on circuit crossing over to the backup circuit.

[Jonestrollingmotor]

Get a battery (you can use one out of the boat) and some jumper wires. connect the battery ground to the trailer in a place that it gets good ground. Using a jumper go from battery positive (use the 5pin plug) to each of the terminals. Brown is running lights, green is right turn and right brake, yellow is left turn and left brake, white is ground (don't touch this one with the positive) and blue is backup/reverse solenoid release. This will verify all the lights and wiring are working on the trailer. Next, disconnect the ground/white wire from the five pin plug to the trailer at the trailer. now, back the truck up to the trailer, do not connect the trailer to the truck and plug it in. You should get nothing. Use a jumper wire, go from a good truck ground to a good trailer ground. The lights will either work as they're suppose to (meaning a bad ground through the plug) or they will work like they were before you were doing the checks, which means the current is backfeeding (as mentioned above) through the ground.