VCCA Home Forums GENERAL DISCUSSION Hauling or Trailering trailer lights

with trailer hooked to truck. lights off turn single works fine . with lights on when left single is on all lights blink same if you use right single all lights blink .left clearce lights don t work .could a clearce lights be the blame. almost new trailer worked last time year ago. thanks

You have a bad ground on the trailer or between trailer and truck.

Yep, I also had the same problem on an enclosed trailer about 12 years ago and it turned out to be a bad ground.

why dothey work ok with lights off . but if you turn lights on all lights blink.if it the ground was bad would n they do it all the time.without tearing all lights out what in best way to find whitch light is ground bad thanks

That is what typically happens with a ground problem.

If you have a bad ground, the little electrons running around will hunt for a way to get back home. They may decide to use another path through another circuit to find a way home.

This type problem is best attacked by unplugging the trailer and work with each circuit at the plug. You can use a spare battery or run a patch from the socket on the tow vehicle. A test light is a good tool to work with on this problem.

Trailers that have aluminum that lights mount on are a serious problem. Electrolysis sets in and causes havoc.

90% of the time the problem is the ground between the truck and trailer. Many trailers use the frame for the ground and the hitch to connect ground to the truck. So first make sure that the ground connection between truck and trailer is good. Others use a tiny wire attached to the trailer frame that connects to the truck. It is common for the connection to corrode. If that is found not to be the case then you will need to check the ground at each light and connection. A jumper wire is all that is required but a VOM or multimeter is best.

still don,t understand finaly gave up. drove to a friend house to help me . when i got there everthing worked fine. friend said maby hitch was rusty from setting up and driveing it moved hitch around on ball.everthing fine now .you would think if it was bad with lights on it would be the same with lights off.

You still have a broken ground wire to be sure block the trailer tongue and connect the light harness to the auto and see what happens

20:33 post from yesterday

07:07 post from today

What part of bad ground connection from truck to trailer don't you understand? Is the problem that you don't understand why the turn signal lights work like they should until the running lights are turned on?

Let me try to help. The explanation is a bit hard for most people to understand. Basically the lights work correctly with the light switch off because the ground is poor but good enough to permit the lights to work (they typically are dimmer than normal but that is not noticed). But when the light switch is "on" the tail light circuit is a better ground than the actual chassis or frame ground. If you notice even though the "tail" lights on both sides are flashing one is much more dim than the other. The running lights are often on the same circuit with the tail lights so they will also flash. That is because the pulsing current flows through the filaments on all those lights. Once there is a better ground than the tail light circuit normal operation is restored.

In your case it was rubbing off the rust, corrosion, grease or other resistance between the truck and trailer hitch. Once that circuit was made the lights will all work normally. The solution is to make sure that the ground between truck and trailer is always good with good clean connections and especially the wire to the frame on the trailer.

Another problem you are sure to have in the future is a light that is dim or does not light. You check the bulb and it is ok. So what is the problem? Can you say GROUND? Yup, the ground on the light or in the socket. I have had the problem so many times that I have actually run a separate ground wire to each light, brakes etc. That way I don't rely on the chassis ground which is sure to go bad! It has virtually eliminated light problems on my trailers.

Great explanation Chipper Dipper. That was very informative!

If I hadn't had the problem umpteen times I would not have known what the problem was. Once I solved the ground problem several times I finally figured out the electrical path that produced the observed effect. It is not readily apparent so takes some real noodle work to understand.

Ya, and it probably really strained your noodle too!

I had the same problem on my enclosed trailer years ago, but it was a problem with the ground on those stupid el-cheapo running lights. Man, I hate those things. Anyway, after establishing a good ground on each light the problem was solved. However, the trailer hasn't been on the road for many years so, no doubt, the ground problem will reoccur if and when the trailer is used again.

I couldn't have said it any better,myself! I have almost lost my respect for anyone that makes them durned useless running lights, every time I check my trailer and one is dim or out I just give it a good whack! most of the time it knocks the crazy thing off sometimes it will work almost until it gets dark. I don't buy new ones because the newer ones are sorrier than the older ones. I have a box of them, I take a rainy day and get them out, solder them up Goop the plastic back together and have one ready for the next trip.

I solved my problems, I replaced all the lights with LEDs and ran a special ground wire to every light. No more of connecting the trailer up each year, and as MrMack says, carrying a stick around to whomp every light.

My cargo trailer has a ground wire in the harness itself that goes from the truck frame to the frame of the trailer. It uses a typical camper style plug but the ground wire is connected.

I hear what you guys are saying on the park lights and running lights for the trailer. They always seem to give problems.

We use coppercoat gasket compound between the trailer and the light assembly. We are put a little silicone around the inside edge of the light assembly to keep water out. The coppercoat will keep the metal from rusting but water will dry out the coppercoat unless you seal it with silicone.

A third method if you have time every year is to put the coppercoat and skip using the silicone.

FYI


If you have a trailer with lights, turn signals, backup lights and an onboard battery that charges from the tow vehicle I would suggest you have this 7 way electrical trailer connection it has a built in ground connector :

7-way RV Tow Vehicle Connector Wiring Color Code
# Color Gage Circuit Function connector interior
1 white 10 common ground
2 blue 12 electric brake
3 green 14 tail/running lights
4 black 10 battery charge (+)
5 red 14 left turn/stop
6 brown 14 right turn/stop
7 yellow 14 auxiliary/back up
NOTE: #7 is the center terminal and currently is most commonly used for backup lights.
7-way RV Travel Trailer Connector Wiring Color Code
# Color Gage Circuit Function connector interior
1 white 10 common ground
2 blue 12 electric brake
3 green 14 tail/running lights
4 black 10 battery charge (+)
5 red 14 left turn/stop
6 brown 14 right turn/stop
7 yellow 14 auxiliary/back up
NOTE: #7 is the center terminal and currently is most commonly used for backup lights.

The following only works if you have a 12 volt battery onboard your RV Trailer or carhauler trailer that is charged by your tow vehicle and the trailer battery is charged!!!
I have a 12 volt battery inside my enclosed car hauling trailer to operate the winch and interior lights.

You may also want to read: Emergency Flasher for RV Travel Trailers & Car hauler trailers Marker Lights

This information applies to RV travel trailers and fifth wheels with the RV 7-way flat-pin type plug. This is the most common type plug found on trailers but your trailer may have another type connector.
Your travel trailer or fifth wheel is broken down on the side of the road at night and you want to take your truck into town for parts or to get help. Wouldn't it be nice if you could leave the trailer marker lights on? Since flashing lights mean caution or emergency it would be even better if you could make them flash.

(It's happened that drunk drivers have driven into the back of a vehicle parked on the roadside thinking they were following traffic. So, using flares along with flashing lights is a good idea.)

Roadside isn't the only place where having flashing lights may be useful. Suppose you're boondocking out in BLM land and need emergency assistance. Maybe you can call for help on your cell phone but how in the world can you give specific directions to your fifth wheel. Those flashing running lights out in the darkness could be the beacon emergency response people need to find you.

I've seen instructions for an emergency flasher that requires you to purchase a female connector, do some soldering and wrap the lash up with electrical tape. Well, as you will see from the illustration below, this way is so easy that anyone can do it and all it takes is a heavy duty 2-pin flasher available at any auto parts store.

The key is to connect the flasher to your trailer's umbilical plug as shown in the illustration. See how the plug is oriented with the square bump at the top. Notice the two white arrows pointing to the top two pins of the plug. The pin on the left is #4 and is the battery charging line. The right pin, #3, supplies power to the license, tail and running lights.





When you want the lights on but not flashing... we use our running lights as makeshift Christmas and party lights... you can use a short length of 12 gauge wire as a jumper to light up your rig

MrMack that is some good information. I will just have to remember it.

Andy, the good thing about this site is you don't have to remember all of the info, you just got to come back here to look it up again, it hardly ever leaves this page!

YOU are Right I just have to remember the site. The mind is an amazing thing.