Diagnosing Dim Camper Tail Lights When Truck Headlights Are On

[Sped1]

TheBar.....

As instructed by you....I did the tests with the parking lights on only. Truck lights perfect, camper has no running or reverse lights, directionals and brake lights for great....

 

[TheBar]

In the left picture there's a lot of rust in the holes in the truck frame. It may not be grounding thru the rust. If you have a piece of sandpaper or even a rough piece of gravel try cleaning up the bolt head below where you have the jumper cable attached, then attach the cable to the bolt head and try again. You may just have to avoid driving at night until you get home and find a friend with electrical experience. LED lights are great but over your 10 years of use they may be just getting dim.

 

[Sped1]

New piece of info.....

Everything works perfectly on the truck....

The directionals and brake lights work on the camper ONLY on when the truck light dial is on AUTO. They do not work when the the dial for the lights is on manual lights on ...or parking lights.

And in one other strange development….
When the manual lights are on, running lights do work on the back of the camper, but they are super dim…. The directionals do not. And on any other setting the running lights and the reverse lights do not work.

 

[Sped1]

Also.....

I swapped out the rear camper from bulbs to LED's lights two summers ago. It's worked perfectly until two days ago.....

The LED's work because when I hit the brake pedal they light up nice......

Also....I tried running all these tests with the house batteries disconnected and it made no difference....

 

[Sped1]

Bolt sanded clean….
Same results ….

I wish there was another way I could measure the ground issue…..

 

[Sped1]

Also.....when the headlight control dial is on AUTO the head and tail lights of the truck don't shine full bright because it's broad daylight and the sensor maybe sees this and keeps on the dimmer setting. When it's on AUTO the truck tail lights are off. When you turn the headlight dial to manual the head and tail lights come on full bright.......

 

[Rene T]

Rene .....A few questions....

I'm a little confused, I'm sorry .....

You say to run these tests on the trailer side plug...That would be WHILE it's plugged into the truck side plug, right?

And...... I'm running the test wire from the trailer side plug to the trucks 7 way connector? Like testing each individual part of the system (left directional etc)?

Don’t do anything on the truck side. Move the truck far away. You don’t need the truck during my test.
It looks like you have a battery in the camper. That red contact on the trailer plug should go directly to your camper battery. Whenever the truck running that’s how your camper battery gets charged.
So that red contact should be powered all the time getting power from your camper battery. Forget about the truck plug.
So if you take my small jumper and plug in one end to the red contact of the trailer plug (so now my jumper will have 12 volt power) and then take the other end of my jumper and plug it into the other contacts. Those lights should come on because you will be powering them from the camper battery.

DO NOT plug that jumper to the white contact because that is the ground. If you did, you would get a lot of sparks.
Also no need to plug the jumper into the blue contact because that would be for trailer brakes which you don’t have.
If all the lights work during my test, then I think you can safely say that there is nothing wrong with camper lights.

 

[Sped1]

So I need to DIY a little “jumper” set up…
What gauge wire should I use for that? What type of “ends” should I have on each end?
From what I understand, that wire doesn’t need to be that long because we’re just testing the other prongs on the same trailer plug…… Powering them by attaching one of the ends of the homemade jumper to the red lead in the 7 way plug and testing the others (tail lights, turn signals brakes, reverse) work.) light up.

But stay away from the white prong when testing….

Am I understanding you clearly?

Also…. Thanks for hanging out with me all day….ha ha ha…..

 

[Rene T]

That is perfect. I use to use a 14 gage romex solid wire. Just remove about a 1/2” of the outer jacket.
No need to check the brake contact because you don’t have brakes.

Have you ever driven in a campground at night and find that some campers have all of their running and taillights lit up. All they are doing is putting a short jumper on the contacts on either side of the alignment key which is the 12 volt power and the running light. It’s just a little decorative to the rv. I’ve played jokes on friends of mine by sticking a short jumper in those two contacts when they aren’t looking and then ask them what’s wrong with their lights causing them to light up

Do you have one of those 12 volt test lights that looks like an ice pick with a light in the handle and a length of wire with an alligator clip on the end. You could stick the pick end of the tester into the red contact then stick the alligator clip in the ground contact. The light in the handle should light up. That is testing the ground. Now that’s not saying you have a perfect ground. You could loose that ground if you have more current. But it would be a good indicator to start with.

 

[Sped1]

That is perfect. I use to use a 14 gage romex solid wire. Just remove about a 1/2” of the outer jacket.
No need to check the brake contact because you don’t have brakes.

Have you ever driven in a campground at night and find that some campers have all of their running and taillights lit up. All they are doing is putting a short jumper on the contacts on either side of the alignment key which is the 12 volt power and the running light. It’s just a little decorative to the rv.

Funny enough....In 26 years ...I've never been to a campground.....

But.........I now understand what you're talking about and I'll buy that wire and try again tomorrow!!

I wonder what the smallest piece of wire I can buy..... smallest I see so far is 15 ft for $20....

Nothing but bare wire touching the contacts is ok?

 

[Rene T]

Have you disassembled the truck side receptacle to inspect the internal wire connections on the backside. That is an area that is known to leak water after several years of use and causing all kind of issues. I would look there if my camper tests shows positive results.

 

[Sped1]

I disassembled the connections at the camper end.....and I can do the truck end of the umbilical cord tomorrow too!

 

[Sped1]

It's dark now so I just retested the lights.....

When the light control knob is on AUTO and manual ON it appears that the running lights are indeed on, but barely, and I mean you can barely see the feint glow of each "node" in each light, Still nothing else works, no brake lights, turn signals, reverse lights....

They all work pretty good when the light knob is in the off position....I'm not sure if there's supposed to be running lights when the lights are turned off like they would be during the day, but the brake lights, turn signals, reverse lights all work.....

I'll get back at to tomorrow......

Thanks to all for trying to help.....I'm a long way from home and I appreciate all the kindness of strangers, who don't need to help at all...... but do...and I'm truly grateful......

Dan

 

[Rene T]

In post #14, you said sorry if these questions are stupid. No need to apologize. No question is stupid. If you don’t know the answer, it’s not stupid to ask no matter how small it may seem to you.

 

[Sped1]

Don’t do anything on the truck side. Move the truck far away. You don’t need the truck during my test.
It looks like you have a battery in the camper. That red contact on the trailer plug should go directly to your camper battery. Whenever the truck running that’s how your camper battery gets charged.
So that red contact should be powered all the time getting power from your camper battery. Forget about the truck plug.
So if you take my small jumper and plug in one end to the red contact of the trailer plug (so now my jumper will have 12 volt power) and then take the other end of my jumper and plug it into the other contacts. Those lights should come on because you will be powering them from the camper battery.

DO NOT plug that jumper to the white contact because that is the ground. If you did, you would get a lot of sparks.
Also no need to plug the jumper into the blue contact because that would be for trailer brakes which you don’t have.
If all the lights work during my test, then I think you can safely say that there is nothing wrong with camper lights.

So I need to DIY a little “jumper” set up…
What gauge wire should I use for that? What type of “ends” should I have on each end?
From what I understand, that wire doesn’t need to be that long because we’re just testing the other prongs on the same trailer plug…… Powering them by attaching one of the ends of the homemade jumper to the red lead in the 7 way plug and testing the others (tail lights, turn signals brakes, reverse) work.) light up.

But stay away from the white prong when testing….

Am I understanding you clearly?

Also…. Thanks for hanging out with me all day….ha ha ha…..

So I performed your tests, but I didn’t use a wire, I used an actual incandescent test light…… I figured that’s good enough, but I can still do it with a wire if you think that’s better…

Using the camper plug only I clipped one end to the red Aux 12v power tab…

I touched other end to the running lights and got nothing…

I touched the other end to the left, turn signal and got nothing…..

I touched the other end to the right turn, signal and got nothing…

I touched it to the center reverse lights and got nothing……

That being said, the batteries do power all the elements inside the camper, heat fan, interior lights, etc.

Does this answer your question?

 

[Sped1]

Just to be thorough …I also did that exact same test with that 14 gauge wire, I got the same results. I can’t get any of the lights to light up on the back of the camper with this test.

 

[TheBar]

One end of the wire goes in the truck plug and the other end in the camper plug. Also the test light won't transmit enough juice through its bulb to light your camper lights. You need a wire.

 

[Rene T]

One end of the wire goes in the truck plug and the other end in the camper plug. Also the test light won't transmit enough juice through its bulb to light your camper lights. You need a wire.

Unless I’m wrong but I believe the OP should have 12 volt power at the red contact all the time when the camper batteries are hooked up. No need of the truck.

To the OP, if I read your post you do have one or two batteries in the camper. Is that correct?
Did you use that test light between the red (power) contact and the white (ground) contact? If that test light is 12 volt, the light should light. Try this test light on a battery to verify it is good.
Do you have a meter? See if there is any voltage between the red contact and the ground contact.

To all members, should there be power at the red contact because that lead goes right to the camper battery. Is that right?

 

[Sped1]

One end of the wire goes in the truck plug and the other end in the camper plug. Also the test light won't transmit enough juice through its bulb to light your camper lights. You need a wire.

This is what Rene T told me to do..... "Don’t do anything on the truck side. Move the truck far away. You don’t need the truck during my test."


SO.......Rene T......I just used the test light between the the red (power) contact and the white (ground) contact...The test light did not light up.....see photo

 

[Rene T]

Try it on a good battery,

Do you have a battery disconnect switch someplace near the battery.

Follow the positive wire off the battery. Is there a inline fuse that may have tripped when you installed the new batteries?

Your cable/pigtail should go to a junction box. Open it up and check the wire nut on the red wire which should be the power wire. Unscrew it and make sure there is no corrosion in the wires. Sometimes just from vibrations, that wire nut could loosen up and the wires disconnect inside the wire nut