Puzzled by trailer lights not working

[drsportster]

Brand new trailer harness installed by me Now I have intermittent power at the output plug This is driving me nuts

 

[rustred]

Brand new trailer harness installed by me Now I have intermittent power at the output plug This is driving me nuts

which output plug ?

 

[rustred]

I'm not understanding here, as we suggested to get a battery and ground the trailer with a booster cable. then go to each input plug terminal off the pos. with a wire and touch each terminal and see if the lights work, as which they should. then you know the trailer is all good. we have no info if you have did that. sounds like you just replaced the harness for just because, ? with out knowing if its bad. and to add brown is tail lights, green right signal, yellow left signal, white is ground, so hooking if you can see the colors then you are double checking yourself it is correct. if the lights work accordingly ,there is nothing wrong with the trailer.

 

[Jim.ME]

Work on one end at a time!

As has been suggested several times; use a battery with jumper wires and test/repair the trailer lights first. If you get the trailer lights working correctly it will narrow the problem to the truck or adapter at the truck socket.

Did you install a purchased 4-wire harness or make your own harness? Did you wire it by a standard diagram (and colors) for a 4-wire harness with the common functions four wires support (Tail/marker lights, left and right signal lights and ground)?

 

[Jim.ME]

deleted duplicate

 

[MarkB_MI]

Brand new trailer harness installed by me Now I have intermittent power at the output plug This is driving me nuts

Just to be clear, you mean you replaced the trailer harness on the tow vehicle? I wonder where that harness picks up its ground.

When you're checking for power at the output plug (receptacle?), are you checking to the vehicle ground or to the ground pin of the connector?

 

[Jim.ME]

Just to be clear, you mean you replaced the trailer harness on the tow vehicle? I wonder where that harness picks up its ground.

When you're checking for power at the output plug (receptacle?), are you checking to the vehicle ground or to the ground pin of the connector?

I read his first post of the thread as the trailer has all new harness and lights. And in his post #41 above he says new trailer harness he installed.

 

[MarkB_MI]

I read his first post of the thread as the trailer has all new harness and lights. And in his post #41 above he says new trailer harness he installed.

Thanks. What threw me off was "intermittent power at the output plug", which would indicate a problem with the tow vehicle. I realize now that the two statements ("new trailer harness" and "intermittent power") aren't related.

 

[rustred]

Brand new trailer harness installed by me Now I have intermittent power at the output plug This is driving me nuts

Communicate with us .

 

[drsportster]

The output adapter plug is intermitent now . If I ground to the trailer it will not light test light only if I ground at liitle prong on the plug adapter Trailer is not grounded somehow to truck from trailer

 

[drsportster]

Work on one end at a time!

As has been suggested several times; use a battery with jumper wires and test/repair the trailer lights first. If you get the trailer lights working correctly it will narrow the problem to the truck or adapter at the truck socket.

Did you install a purchased 4-wire harness or make your own harness? Did you wire it by a standard diagram (and colors) for a 4-wire harness with the common functions four wires support (Tail/marker lights, left and right signal lights and ground)?

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Good stuff Helpful !

 

[Jim.ME]

The output adapter plug is intermitent now . If I ground to the trailer it will not light test light only if I ground at liitle prong on the plug adapter Trailer is not grounded somehow to truck from trailer

Take the adapter out of the truck socket. Check to see if the ground in the truck socket is good by turning on the truck parking lights and checking between the parking (tail) light blade and the ground blade with a test light or voltmeter. The picture below shows you which blade does what to aid you in testing the socket.

Then test with the adapter plugged in between the ground and taillight terminals of the adapter output.

If those things check out the problem is in the new harness and lights, you installed on the trailer, not your vehicle (which you have told us works fine with the other trailer).

With the trailer unhooked from the vehicle, use a battery and jumper wires to test the trailer wiring. One of the drawings I posted the other day shows you which wire from the trailer plug goes to which light(s). Use the ground terminal of the trailer plug and the plug terminals for testing to check the entire circuit.

If you have a sealed beam headlight, make a test light using it. Using one made that way would draw more current and can make a circuit the test fail if it has bad connection or wire and is not carrying amps enough for the lights.

You keep saying taillights, does this include turn signal/brake lights and marker lights?

What did you install for a harness? One of the ones with the wires made to the flat 4-pole plug and the wires are long enough to reach the length of many small trailers. Or a flat 4-pole plug with short pigtail wires that you spliced other wires to for going to the taillights. Did you use and follow a trailer wiring diagram like the one I posted.

Whether you do the vehicle first or the trailer first, fix one then go to the other. Jumping back and forth does not seem to be getting you anywhere.

And let us know what results your testing gives; some two-way communication can generally work through things quicker; we can't see what you have done, you have to tell us.

Edited spelling

 

[john in la]

I ain’t touching this with a 10 foot pole.
To much trying to figure out what the problem is.

If you have intermittent power at the output plug I read that as the truck plug.
If you have problems at the truck plug why are we even talking about a trailer.
You need the truck to work properly before you can include a trailer into the equation.

 

[Ray,IN]

Brand new trailer harness installed by me Now I have intermittent power at the output plug This is driving me nuts

It's less confusing to refer to the truck plug and trailer plug instead of outlet and inlet.
Just to be sure, are your plugs flat or round and number of contacts?

 

[MarkB_MI]

From what you have, I assume your tow vehicle has a seven-pin round trailer connector and the trailers use four-pin flat connectors. And between the two you have an adapter that has the little LEDs to tell you when there's power at the adapter. I also assume you have some sort of multimeter to check voltages.

Back in your electrician days, I'm sure you ran into cases where voltage looked good before you put a load on it, but there wasn't sufficient voltage under load. I think you need to check for this, and one way you can do it is to make a breakout cable, which is just two connectors wired together. And they sell them already made up at your local auto parts store. All you have to do is scrape a little insulation off each wire so you can probe it to see the actual voltage that the trailer sees coming out of the tow vehicle. Insert the cable between the 7-to-4 pin adapter and the trailer's connector and start probing.

 

[Jim.ME]

A Recap:

This started with drsportster telling he got a new to him kayak trailer with a new harness and new LED lights. The lights did not work when plugged to the vehicle. However, his ATV trailer lights do work when plugged to his vehicle, (Which would indicate a problem with the new trailer.) and he has said there is power at the vehicle the adapter has a light showing power.

From his replies in this thread:

He is using an adapter. RV/utility type 7 flat blade to 4 pin flat, in the vehicle connector socket. (There is a thread about him having problems connecting a trailer and getting an adapter back in January.)

In post #41 we found out he installed the lights and harness on the trailer.

To be determined:

He has posted there is power at the lights, but they don't work. He has not told what tool(s) he is using or any of his testing methods, beyond the LED lights would not light using a battery charger. It has been suggested he use a battery to test the lights and get the trailer lighting working correctly, then plug it to the vehicle.

He has not told us how he has confirmed the ground circuit between the vehicle and trailer then back to the lights. And from his post #50 it would appear there may be a ground issue.

The intermittent power just appeared in his posts # 41 and 50.

More timely and precise feedback on tests, methods and results would help.


Just my opinion but there is too much jumping around. I use a battery and one of the standard wiring diagrams for the plug the trailer is using when wiring a trailer. Get the lights working properly using the battery. Then plug it to the vehicle once they are working, especially if one knows the vehicle is not a problem when hooked to a different trailer. If the vehicle wiring works on other trailers, there is no need to add it into the mix when installing a wiring harness and lights on a trailer, plugging it to the vehicle is the test at the end.

 

[Jim.ME]

It's less confusing to refer to the truck plug and trailer plug instead of outlet and inlet.
Just to be sure, are your plugs flat or round and number of contacts?

Plugs don't plug into plugs. Socket or connector for the vehicle end is correct terminology and is less confusing than output.

 

[Ray,IN]

Plugs don't plug into plugs. Socket or connector for the vehicle end is correct terminology and is less confusing than output.


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Your're correct; I tried to dumb it down since his replies are so confusing. He should leave the truck and old trailer alone and concentrate on wiring the new trailer properly. For him, I suspect he should take the trailer to either an RV store or Uhaul and have it wired correctly.

 

[buickanddeere]

One trailer is getting a ground through the hitch and the other is not.

A chassis return or “ ground “ through a hitch is not really an electrical connection .

 

[Ray,IN]

A chassis return or “ ground “ through a hitch is not really an electrical connection .

That is technically correct and I never use that, however using the sheet-metal & drivetrain of a tractor for ground is almost universal, and often causes electrical issues with old tractors.