Trailer lights.

[04fxdwgi]

Re: Trailer lights.

Absolutely a bad ground (or maybe a bulb socket ground).....................

 

[N1265]

Re: Trailer lights.

I am talking about the two red tail lights on the trailer.

I did not notice if the tail lights on the truck also dimmed.

I did not noticed if the side marker lights on the trailer dimmed, But I will say that if they did it was not as noticable as the dimming on the rear trailer tail lights...

 

[kenmyfam]

Re: Trailer lights.

I am talking about the two red tail lights on the trailer.

I did not notice if the tail lights on the truck also dimmed.

I did not noticed if the side marker lights on the trailer dimmed, But I will say that if they did it was not as noticable as the dimming on the rear trailer tail lights...

Re-tighten all the bolts holding your trailer together. Seen that prevent good ground connections before............mine to be exact !!!

 

[Jetwash]

Re: Trailer lights.

Can't really put it plainer than that !!!!
Unless I put it this way ......

Bad ground, Bad ground, Bad ground, Bad ground etc

Not true. Not even close.

A short to ground is common for old wires and it can be located in the plug or anywhere back to the light. I pinched a couple wires with a new bolt and shorted out most of the lights.

A short to power will send current to the wrong location or give you bleed over. Bad contacts at the bulb also create resistance

Resistance created by corrosion or hot wires will create low voltage situations that will create the dim bulb effect.

 

[NYBo]

Re: Trailer lights.

Not true. Not even close.

A short to ground is common for old wires and it can be located in the plug or anywhere back to the light. I pinched a couple wires with a new bolt and shorted out most of the lights.

A short to power will send current to the wrong location or give you bleed over. Bad contacts at the bulb also create resistance

Resistance created by corrosion or hot wires will create low voltage situations that will create the dim bulb effect.

A dead short will blow a fuse, not cause the dimming the OP is experiencing. This is almost definitely a ground problem.

 

[N1265]

Re: Trailer lights.

Ok, I got some time to do some work on this today.

First, I just went ahead and and ran ground wires to the side marker lights and tapped them into the white ground wire for the trailer harness, so now all four lights are tapped into this wire witch is also bolted to the frame of the trailer itself.

But the condition did not change, This is when I noticed that the truck tail lights also dim ( running lights on, turn signal on, opposite side of flashing turn signal dims with flash ) However, the condition is not as noticable on the truck as it is on the trailer.

I unplugged the trailer, but the truck lights still slightly dimmed.

I switched the flashers ( turn / emergency ) but this had no effect.

I gave it a higher idle, but this also had no effect.



So now what ?

 

[Grandad]

Re: Trailer lights.

This is when I noticed that the truck tail lights also dim ( running lights on, turn signal on, opposite side of flashing turn signal dims with flash ) However, the condition is not as noticable on the truck as it is on the trailer.
So now what ?

I still think your problem is a poor ground path, but now it obviously must be in the truck's wiring system. I know, not likely in a nearly new '77. Have a close look at the cable joining the body of your vehicle to the negative battery post. This would not likely be the same wire that grounds the engine. I assume you're not having any problem with cranking over the engine, so that cable must be OK. Not familiar with your truck model. Sometimes the body ground cable runs from the negative post to the firewall, fender or radiator support, but it could also be a jumper from the engine to the body in an obscure location. I had a Dodge van (even newer than your truck) that had a flexible braided strap forming part of the ground system that entirely corroded away and needed to be replaced to cure a number of electrical problems.

 

[GA_Boater]

Re: Trailer lights.

Ok, I got some time to do some work on this today.

First, I just went ahead and and ran ground wires to the side marker lights and tapped them into the white ground wire for the trailer harness, so now all four lights are tapped into this wire witch is also bolted to the frame of the trailer itself.

But the condition did not change, This is when I noticed that the truck tail lights also dim ( running lights on, turn signal on, opposite side of flashing turn signal dims with flash ) However, the condition is not as noticable on the truck as it is on the trailer.

I unplugged the trailer, but the truck lights still slightly dimmed.

I switched the flashers ( turn / emergency ) but this had no effect.

I gave it a higher idle, but this also had no effect.



So now what ?

That's why I asked if the truck lights dimmed also cause I was starting to think it's the truck, not the trailer. Grandad said about the braided ground, also I seem to remember that my rear lights had a ground from the socket to the body. I'll have to pop a light assembly off my 87 Ramcharger tomorrow to verify. I remember some other grounds, I'll check those too. My trailer and truck lights are perfect, now if it only got more than 11 mpg!!

 

[Jetwash]

Re: Trailer lights.

Hi Guys,

I am just wondering why one side of my running lights dim down, when the opposite side has the turn signal on ?

It does it when either the left or right turn signal is on .

Lets run through this again. If the lights dim, when you turn on other lights, its because they are using up some of the current going to those bulbs.

When you have more than one bulb in line between the positive and the ground, the voltage and current is divided between both of the bulbs. They will be dimmer than one single bulb. In every circuit, the voltage is used up. Its either used up by lights, shorts or resistance (thats what resistors do) as well as rheostats and other mechanisms that reduce current. A poor connection will create resistance.

If you had a bad ground, you would always have dim lights, not just when you turn on the blinkers. If you want prove you have adequate grounding, run a jumper cable from your boat trailer to your vehicle.

I dont know how long you had the trailer, but its possible that the turn signals and the marker lights have some kind of connection. A frayed wire or split end might allow a single strand of wire to contact a separate surfaces. If anyone worked on the trailer, but not even the lights, it could become a problem.

When in doubt, go back to the basics. Check each circuit on the truck plug. Check for frayed wires on both sides and in the junction box if one exists.

 

[GA_Boater]

Re: Trailer lights.

We did - the prob is in the tow vehicle, not the trailer. It's a lot easier to make sure all the ground connections are right before moving to voltage leaks. My dvm leads aren't long enough to reach to his truck or this would be fixed.

 

[kenmyfam]

Re: Trailer lights.

We did - the prob is in the tow vehicle, not the trailer. It's a lot easier to make sure all the ground connections are right before moving to voltage leaks. My dvm leads aren't long enough to reach to his truck or this would be fixed.

+1 on this ^^^^^^^

 

[kenmyfam]

Re: Trailer lights.

Not true. Not even close.

A short to ground is common for old wires and it can be located in the plug or anywhere back to the light. I pinched a couple wires with a new bolt and shorted out most of the lights.

A short to power will send current to the wrong location or give you bleed over. Bad contacts at the bulb also create resistance

Resistance created by corrosion or hot wires will create low voltage situations that will create the dim bulb effect.

Changed you mind yet ???? :facepalm:

 

[04fxdwgi]

Re: Trailer lights.

"But the condition did not change, This is when I noticed that the truck tail lights also dim ( running lights on, turn signal on, opposite side of flashing turn signal dims with flash ) However, the condition is not as noticable on the truck as it is on the trailer."



The hi-lighted statement just said volumes of the problem. If there is a problem in the truck wiring, it will be intensified when trailer is connected. Could even start melting some things with the added load.

 

[GA_Boater]

Re: Trailer lights.

Hey N1265 - I just checked my truck. Behind the tail lights a ground wire goes from the socket to a screw in the body. My tail light housings are plastic so the lamps need a dedicated ground. I'm not sure if you have plastic or metal housings, but still worth a check that the screw and lug are bright and clean. And check the braided ground from the engine to the frame. One more thing - remove and check each of the truck bulbs, in the tail/brake and the front also. A bulb or socket may be corroded. Let us know how you make out.

 

[Jetwash]

Re: Trailer lights.

Changed you mind yet ????

Why would I. Its not a ground connection on the trailer.

It wont be a ground connection in the truck, either.

 

[wifisher]

Re: Trailer lights.

Lets run through this again. If the lights dim, when you turn on other lights, its because they are using up some of the current going to those bulbs.

When you have more than one bulb in line between the positive and the ground, the voltage and current is divided between both of the bulbs. They will be dimmer than one single bulb. In every circuit, the voltage is used up. Its either used up by lights, shorts or resistance (thats what resistors do) as well as rheostats and other mechanisms that reduce current. A poor connection will create resistance.

If you had a bad ground, you would always have dim lights, not just when you turn on the blinkers. If you want prove you have adequate grounding, run a jumper cable from your boat trailer to your vehicle.

I dont know how long you had the trailer, but its possible that the turn signals and the marker lights have some kind of connection. A frayed wire or split end might allow a single strand of wire to contact a separate surfaces. If anyone worked on the trailer, but not even the lights, it could become a problem.

When in doubt, go back to the basics. Check each circuit on the truck plug. Check for frayed wires on both sides and in the junction box if one exists.

Let's go through it one more time. If the light dims when an additional light is turned on, it is a bad ground. This is by far the most common lighting problem on vehicle lighting systems other than burned out bulbs. There are several circuits feeding power to the different lights on any vehicle. This is why they can come on at different times. However, the ground portion of these circuits is often shared by multiple power sources. If there is a problem with the shared portion of the circuit, the symptoms are displayed when both circuits are used simultaneously. The lights dim because the ground path can not handle the extra current that is being applied to it. Remember that the voltage does not do the work. The current does. If you limit it, you will get less work done.

 

[N1265]

Re: Trailer lights.

And check the braided ground from the engine to the frame. Let us know how you make out.

I can find no braided ground strap from the engine to the frame, could of sworn there was one there before. do they run from the back of the right head to the frame on these older Dodge trucks ? or am I thinking of another vehicle I have owned. I just replaced the exhaust manifold gasket on this truck a couple of months ago. Maybe I took it off at that time and never put it back on. Altho I think I would not of forgotten something like this, It is not uncommon for me to have extra parts left over after working on things.

The tail light housings on my truck are metal and I just cleaned them 2 months ago and surround them with dialectric grease. same with the ground wires for the front turn signals that mount to the radiator support, the ground wire to the engine from the battery, the ground wire from the fender to the battery. I have not checked the sockets yet.

If I remember right, The turn signals from my plow mount ground threw the plow frame, witch are grounded threw the frame of the truck. With no ground strap present to the frame of the truck, could this be the problem with the dimming lights even though they still work ?

 

[wifisher]

Re: Trailer lights.

If you are not sure if there should be a ground strap there, just add one. You can not hurt anything by over-grounding. You will find that when you add it to the right place, the lights will work properly.

 

[N1265]

Re: Trailer lights.

Would a 10 ga wire ran from the battery straight down to the frame be a big enough replacement for a missing ground strap ?

 

[NYBo]

Re: Trailer lights.

When you have more than one bulb in line between the positive and the ground, the voltage and current is divided between both of the bulbs.

This is a description of bulbs wired in series, which is NOT the case here.They are in parallel. A long as the circuit is able to provide adequate amperage (current), the bulbs will remain at the same brightness level.

To the OP: Have you checked the charging system in the truck?