Trailer Lights, Possible Ground Problem

tchapmond · 10-22-2012, 05:15 PM

My tow lights do not work unless the trailer is attached to the tow vehicle. It appears that the lights depend on the attachment for the ground. It seems like it should be getting a ground from the white wire that comes from the truck that is connected to the white wire in the trailers electrical harness. My question, is there a ground wire somewhere on the trailer? I have a 25RK bumper pull.

Thanks.

**Crabman** · 10-22-2012, 05:21 PM

Welcome to the forum. It is normal for the trailer lights to not operate without being plugged into the tow vehicle unless the 7 pin connector is "jumped". See this link:

http://www.jaycoowners.com/showthrea...connector+jump

LongIslandCamper · 10-22-2012, 05:35 PM

Quote:

Originally Posted by Crabman

Welcome to the forum. It is normal for the trailer lights to not operate without being plugged into the tow vehicle unless the 7 pin connector is "jumped". See this link:

http://www.jaycoowners.com/showthrea...connector+jump

What he said.

ChooChooMan74 · 10-22-2012, 05:55 PM

I think he is saying is that the ground between his TV and TT is broken and that the hitch makes the ground. Totally unsafe with an unreliable ground with the trailer brakes.

How I would diagnose? Meter is my tool. I would take the ground pin on the tv and the tt and touch a phisical piece of chassis. Whichever is open or high resistance, I would wire a new ground to.

**Crabman** · 10-22-2012, 06:16 PM

Quote:

Originally Posted by ChooChooMan74

I think he is saying is that the ground between his TV and TT is broken and that the hitch makes the ground. Totally unsafe with an unreliable ground with the trailer brakes.

How I would diagnose? Meter is my tool. I would take the ground pin on the tv and the tt and touch a phisical piece of chassis. Whichever is open or high resistance, I would wire a new ground to.

Yep, I see your point. My mistake.

tnchuck100 · 10-22-2012, 07:08 PM

My take is Crabman had it right the first time.

He states the lights work when hooked up to the TV. That's normal.

Tow lights do no work when unhitched.

Hopefully he will return and clarify the issue.

tlhdoc · 10-22-2012, 07:10 PM

Quote:

Originally Posted by tnchuck100

My take is Crabman had it right the first time.

He states the lights work when hooked up to the TV. That's normal.

Tow lights do no work when unhitched.

Hopefully he will return and clarify the issue.

2X

tchapmond · 10-22-2012, 08:28 PM

I am back. If I plug the lights and brake in without hitching the trailer to the tv, the lights don't work. Once I hitch the trailer the lights work. I wondered if there is an independent ground on the trailer that might have come loose, causing the need for the hitch to become the ground. Hope that clarifies the issue.

ChooChooMan74 · 10-22-2012, 08:56 PM

I thought this was the issue. I like taking simple measures. Do you have a meter or a test light? Look at this diagram..

Meter with Ohm or Continuity tester
Take Pin 1 and touch a good ground on the TV or Trailer. You should get Continuity. If you don't on either the TV or Trailer...or both, then I would look into where the wire is broke or just run a new ground.

Test lite
Take the test lite to pin 4 and test both to pin 1 and to a good ground on both the TV and the trailer. See if the test light illuminates. If between pin 4 and 1, on either the TV or the trailer, the light does not illuminate, you found where your problem is.

That is my way of diagnosing. Everyone has their own method that works well for them.

tchapmond · 10-22-2012, 11:45 PM

When you say run a new ground, do you mean abandon the white wire on the trailer? By the way, the brakes have worked even when the lights don't.

robo59097 · 10-23-2012, 04:41 AM

The TT must be atached to the TV hitch to complete the ground for the taillights

tnchuck100 · 10-23-2012, 04:55 AM

Quote:

Originally Posted by tchapmond

I am back. If I plug the lights and brake in without hitching the trailer to the tv, the lights don't work. Once I hitch the trailer the lights work. I wondered if there is an independent ground on the trailer that might have come loose, causing the need for the hitch to become the ground. Hope that clarifies the issue.

This has me questioning your set up. You say you plug in the lights AND brake. Do you have two separate connectors? That would only partially explain the brake working but not the lights. The ground ground for the running lights, the brakes, the trailer frame and the white wire of the 7 way connectors should be common. It sounds like you have a modified system if you have two connectors. That being the case trouble shooting from here is going to be tough.

If you, in fact, have the single 7 connector plug following ChooChooMan74's steps will lead you right to the problem.

Please clarify the "plug in the lights AND brake" issue.

tnchuck100 · 10-23-2012, 05:00 AM

Quote:

Originally Posted by robo59097

The TT must be atached to the TV hitch to complete the ground for the taillights

This is NOT the way it is supposed to be. The ground should be through the connector (white wire, pin 1) this connects the TV frame to the trailer frame. Any other configuration is incorrect.

robo59097 · 10-23-2012, 05:41 AM

Now that I think about it your right, I was thinking on the rental trailers we use to have we ran a separate ground that required the trailer to be hitched

Quote:

Originally Posted by tnchuck100

This is NOT the way it is supposed to be. The ground should be through the connector (white wire, pin 1) this connects the TV frame to the trailer frame. Any other configuration is incorrect.

tchapmond · 10-23-2012, 07:19 AM

Quote:

Originally Posted by robo59097

Now that I think about it your right, I was thinking on the rental trailers we use to have we ran a separate ground that required the trailer to be hitched

Sorry I confused things. I definitely just have a 7 pin connector. When I was pulling the trailer, the brakes worked but the lights did not.

When I got home, I took a simple 12v testor and checked power coming from the truck. With the emergency flashers on and grounding the testor to the body, I confirmed power from the two pins (6 & 5/yellow & brown). I then took the sheath off of the 7 pin connector on the wires coming from the trailer. I took each wire loose cleaned them up and reconnected them. I then did what I could to clean the contacts in the plug. I was able to get power on 6 & 5 on the trailer side with the ground from the testor connected to the truck; however, the lights were still not working. I then hooked the trailer via the hitch and I had lights.

I feel pretty sure that ChooChooMan74 is correct. My trailer is not at my house, so I wil do as he suggested when I get back to the trailer. It does seem weird that the brakes worked and the lights didn't - I agree, if the ground wasn't connecting through the white wire from the truck, it seems that the brakes should not have worked either.

So, if I do the diagnostics suggested by CCM74 and I find the ground is the problem (which I suspect), how do I run a new ground. The white wire going to the trailer is in the bundle of 7 wires. Do I abandon the white wire in the bundle and run a separate wire? And the biggest question that I still don't understand is: Where does the white ground wire in the bundle connect to the trailer? I assume it connects to the frame somewhere? I am hoping that that connection has just come loose and I can reconnect it, negating the need to run a totally new wire.

I really appreciate your enthusiasm for helping me out.

tnchuck100 · 10-23-2012, 07:45 AM

With the trailer connected to the TV but NOT hitched up, take a wire and connect it to the TV frame and the trailer frame. Do all the lights work? If so either the pin 1 wire in not connected to the frame of the TV or at the frame of the trailer. It just a matter of finding where the frame connections are made. Replacing the wire should not be necessary unless it has actually been cut. It is most likely a loose or corroded connection at the TV or trailer frame.

When you finally find and fix the problem you should keep the connector (both pieces) clean and periodically spray them with WD-40. That will cut down on corrosion problems greatly.

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