Diagnosing Dim Camper Tail Lights When Truck Headlights Are On

[Sped1]

When the truck headlights are off, the camper lights (brake, directional) work perfectly....

When the truck headlights are in the on position, the tail lights go do dim and you can barely see them......

Thoughts?

Separate question.... Do the house batteries have ANYTHING to do with the camper tail lights?
I just put two new house batteries in and they seem to be WEAK, can't get the voltage passed 11.7.......
But....I just don't think the two things are related.......

I'm on the road 1,400 miles from home so I'd love to have a plan to tackle these issues......
Right now the camper taillights are the priority.....

Thanks in advance..... Dan

 

[bigbAZ]

When the truck headlights are off, the camper lights (brake, directional) work perfectly....

But do the tail lights work too?

When the truck headlights are in the on position, the tail lights go do dim and you can barely see them......

Thoughts?

And what about the brake and turn?

Separate question.... Do the house batteries have ANYTHING to do with the camper tail lights?

No.

Also what year is the truck and are the headlights incandescent or LED? My first thought is you have a grounding issue and the camper lights are grounding through the headlight filaments (if incandescent) then when you turn them on the series circuit dims the tails.

To test this theory simply bring a good ground wire to one of the tail lights and touch it to the metal.
Or:
Often the tail lights are attached to the aluminum skin with sheet metal screws and that's all the grounding they get. removing the red lens and slightly tigening those screws can fix it.

 

[Sped1]

Answers to your questions.....

2020 Ram 2500.....The lights have bulbs so...Incandescent
The camper lights are LED.....asnd up until yesterday, worked perfectly for the last 10 years....

When the truck headlights are off, the camper lights (brake, directional) work perfectly....

But do the tail lights work too?
No, Because the headlights are off I'm assuming.....

When the truck headlights are in the on position, the tail lights go do dim and you can barely see them......

Thoughts?

And what about the brake and turn?
YES.....but they are so dim you can barely see them.....


You said......"Bring a good ground wire to one of the tail lights and touch it to the metal...
A good ground wire to one of the tail lights of the truck or the camper? and touch it to the metal of what? The camper or the truck (frame?)?

Thank you 1000 times bigbAZ.....I'm so grateful you took the time to answer my post........

Dan

 

[bigbAZ]

To find a bad ground sometimes the best way is to attach a wire to a good ground and make contact with any metal parts of the tail lights or side markers to see if it fixes the issue, then you know you have a bad ground. You can run it from the truck just to any good clean metal on the camper first just to rule out the ground connection at your connector, then try touching it to any unpainted metal parts of the lights. You may have to remove a lens to get to bare metal. If the ground is good from the truck to the camper then you can use the camper metal for your ground source.

 

[Sped1]

When you say "Run it from the truck" all I need to do is run the wire from some part of the frame of the truck (trailer hitch receptacle for example) to any part of the frame of the camper ( metal piece where you attach the tie-downs)

Can I use a set of jumper cables to do these tests? Well, like just the single red section of the cable? Because I already have them?

THANK YOU, THANK YOU, THANK YOU!!!!!!!!!

 

[bigbAZ]

When you say "Run it from the truck" all I need to do is run the wire from some part of the frame of the truck (trailer hitch receptacle for example) to any part of the frame of the camper ( metal piece where you attach the tie-downs)

Can I use a set of jumper cables to do these tests? Well, like just the single red section of the cable? Because I already have them?

THANK YOU, THANK YOU, THANK YOU!!!!!!!!!

Yes a jumper cable will work fine. So the problem is not the headlights but rather the tail lights since when you turn on the headlights it also turns on the tail/running lights. I suspect that your brake and signal lights are finding their ground through the tail lights and when the tail lights get switched on it puts them is series with the brake/turn lamps which reduces the voltage and dims everything. You might look around for any ground wires that could be loose or corroded.

 

[Sped1]

Got it!!!

I'll test it all tomorrow morning!!!!

I thankful for the kindness of strangers........Seriously.

 

[TheBar]

First - with the camper not plugged into the truck are the truck tail lights dim?

Assuming the truck lights are ok, to me the biggest clue is you just put two new house batteries in and you can't charge them past 11.7. Find the cause of this and likely find why the tail lights are dim.

Most likely is a bad ground between the camper and truck would mean the truck alternator is not charging the batteries.

If you use a jumper cable between the truck frame and camper remember the metal parts of the camper frame may not be connected to the camper electrical system. If possible run the jumper cable directly to the unpainted part of the light housing. Or if not long enough connect both the red and black jumper cables together to extend to the housing.

If that works, look at your truck to camper plug to see if there is any corrosion or damage in the plug. Then check the ground screw/bolts on both the truck and camper cables to make sure they are tight where they attach.

OR - the cables on the house batteries are corroded or not connected properly at one end or the other.

Or - since the camper is LED and the truck is not (are you sure about that?) there is likely an LED converter in the circuit that may be bad.

OR - one or both batteries are faulty and overloading the whole electrical system.

Are you using a separate charger on the new batteries? If so are both charger leads attached directly to the batteries? Are you sure the charger is good. Have you tried charging the batteries separately or both together at once.

The headlights are a bigger draw on the electrical system than any of the other lights. A weak electrical system is why the lights may seem dimmer when the headlights are on.

 

[Sped1]

"First - are the dim tail lights the truck or camper tail lights?"
Only the camper lights, and only when the truck lights are turned on (at night).

"Are you using a separate charger on the new batteries?"
I have no charger beyond a solar panel, and the truck alternator charging while driving......

I have not attempted to charge batteries at all with an actual charger. I've NEVER had to do that and have always (until these new batteries) relied only on the truck charging while driving and the solar panel.

I'll go thru the wiring of the batteries tomorrow again. When I put these new batteries in I took pics of the old ones before removing the wires.......

I think it's a bad ground...... I'll run some tests tomorrow.......and let you know what I find....

Thank you The Bar!!!!!

 

[CharlesinGA]

Bad ground plain and simple. Where the 7 way harness connects inside the camper, at the 7 way plug, at the truck's 7 way receptacle (poor connections) or a wire partially worn thru, or bad connection in the trucks connector on the backside of its 7 way receptacle.

Very probably a poor connection at the 7 way itself, prongs just not making good contact.

Charles

 

[Sped1]

Thank you Charles!!!!!!!!!!

 

[CharlesinGA]

RAM trucks use relays to operate the trailer tail lights. The truck is NOT sensitive to whether it is LED or incandescent because it is battery direct thru the relays to the 7 way. Even my 2003 RAM 2500 is done this way (in fact mine has "undersized" 20 amp relays that in 2005 they went to 30 amp on. I have a set of 30 amps and a video on how to install them, but I am yet to have an issue with them).

My trailer is now 100% LED lighting now that I have replaced the tag light, and the truck don't care, but I tried to change the TRUCK's tag lights to LED lamps in the sockets and it didn't like it right off. I now have a set of complete LED tag lights coming from Boost Auto that the truck will be happy with.

Supposedly the RAM 7 way receptacle in the bumper is not happy with Bargman 7 way plugs on the umbilical cable. I have read this a number of places and the OEM bumper receptacle is a Pollock and the design does not properly accept a Bargman plug, dunno, mine work.

Bargman type plug on the left, Pollak type plug on the right. (image from Fayette Trailer)

Make sure the contacts in the plug and bumper are clean and shiny, and make sure if you have the Bargman type plug that the blades are squeezed together

 

[Rene T]

I would get a small piece of fairly heavy jumper gauge wire about 6” long and strip both ends back about 1/2”.
Then using Charles schematic in post #10 showing the trailer side plug, insert one end of this jumper into the red (power) contact then insert the other end of this jumper into the brown contact. All your camper running lights and tail lights should now be on and bright.

If all lights look good and bright, leaving the end of the jumper in the red (power) contact, insert the other end into the green contact for the right brake/turn signal and see how those lights look.
Do the same for the yellow contact for the left brake:turn signal.

Then do the same for the purple contact for the backup light.

Let us know what you come up with.
I’m not an electrician but this is what I use to do to check all my truck camper/trailer lights before traveling.

 

[Sped1]

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)?

They way you worded it, it could seem like I'm putting the test wire back into the trailer side plug instead of the trucks 7 way connector......

Sorry if these questions are stupid.......

 

[TheBar]

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)?

They way you worded it, it could seem like I'm putting the test wire back into the trailer side plug instead of the trucks 7 way connector......

Sorry if these questions are stupid.......

I think he meant one end of the jumper wire into the red plug of the truck side and leave it there (might need to turn the ignition key on in the truck). Then the other end into the brown socket of the camper plug. The intention is to make sure the tail lights are getting full positive power. Then move the jumper wire to the other light contacts in the camper plug.

BUT, I would test the ground first with a jumper cable end on an unpainted bolt on the truck hitch or frame, then the other end to the unpainted area on the camper tail light. If the lights are bright then your camper ground needs to be fixed and the other tests don't need to be done.

 

[Sped1]

Where on this completely sealed LED taillight would you test the ground?

Is literally no metal at all showing….

 

[Rene T]

Do you have a battery in the camper?

 

[TheBar]

Where on this completely sealed LED taillight would you test the ground?

Is literally no metal at all showing….

Your only choice then is try touching the jumper wire to different metal spots on the camper and the ground post in the camper plug. The black wire is most likely the ground.

If you have a Walmart, Harbor Freight, or auto parts store near you buy a multi meter. With it you can find the trouble spot easier. Every RV owner should carry one.

 

[TheBar]

Are the truck tail lights also dim?

Do this check also, check the tail lights with the truck light switch in the "parking lights" position instead of the headlight position. That reduces the power draw of the headlights. If the tail lights are bright that rules out a bad ground and may be the positive power wire system.

 

[Sped1]

So.....

I’ve been monkeying around with the system now for about two hours…

The first thing I should say is that the running lights and reverse lights do not work at all. They might be so dim that I can't tell weather they are on at all but I'd say the are now completely off.....I'll check it again at night because they could be so dim......

The first thing I did was attend to the 7 way connections at either end of the umbilical cord. I either spread the prongs out on some or I bent the prongs in so that maximum contact could occur. I put dielectric grease on every part of the connecting metal pieces…..

The next thing I did was to test the ground like you’ve all been telling me…

I attached one of my jumper cables firmly to the frame on the under side of the truck and attach the other end of the jumper cable to various spots on the camper (see photo)…… it made no difference at all.

All the truck lights work perfectly….
All the camper lights work perfectly, except the running lights and the reverse lights when the headlights are on……

I’m definitely intimidated by that multimeter…… that knob has about 75 different settings and the whole thing in general has about four different switches. I wouldn’t have the slightest idea what position to have any of those switches or that knob in. That has to be simplified.

Then there is the issue of the new house batteries…… I still don’t think they have anything to do with the problem, nevertheless, I checked to make sure that they were wired in series correctly. They are……

I have 12.6 V now on the house batteries. The voltage does not increase at all when starting the truck……..

Bottom line…. I still have no rear tail lights or reverse lights when the headlights are on……. Brake lights and directionals work fine.

Now I’m just sitting in the parking lot contemplating life itself….

What next?