One tail light is too bright!

[Kevin A]

I've been working on the Burro (1978 model) we recently purchased and I notice that the left tail light is much brighter than the right one and nothing lights up when the brakes and turn signals are used. It seems that both filaments are turned on all the time, rather than activating when necessary. I check in the housing and that is clean. Does this mean it has a bad ground or a wire hooked up to the wrong feed wire? Any thoughts would be appreciated before I have to start diving into the storage holes to trace the wiring.

Kevin

[Pete Dumbleton]

The top three causes of lighting problems with odd symptoms are:

1. Bad grounding

2. Bad grounding

3. Bad grounding

One way to troubleshoot for bad grounding is to get a long piece of wire, attach it to a ground point on the tow vehicle and put a spring clip on the other end to ground the various light fixtures.

[Gina D.]

I dunno Pete.

I am thinking it's more related to Bad Grounding.......

off to my room

[Byron Kinnaman]

The top three causes of lighting problems with odd symptoms are:

1. Bad grounding

2. Bad grounding

3. Bad grounding

One way to troubleshoot for bad grounding is to get a long piece of wire, attach it to a ground point on the tow vehicle and put a spring clip on the other end to ground the various light fixtures.

I keep hearing this, so I must ask the questions.
What is ground?
How does ground (electrical) relate to a fiberglass trailer?

[Byron Kinnaman]

The only thing that can cause both filiments to light up when just the lights are on is there is a connection to the brake filiment someplace.

The first thing to look at is the lamp bulb fully seated in the socket. If it's not turned all the way so the locking pins are in the proper place it's possible to make connection to both filiments.

Check the wiring around the socket and the socket.

There should be two connections in the back of the socket for the two connections on the bottom of the bulb. Any piece of metal between the two connections will cause both filiments to light.

[Benny K]

Not having the bulb in the socket properly as Byron stated is very common and I won`t tell anyone how I know this.. ...now back to Ground....the best I could find out on Ground is that..... Ground is a common term for the return path in an electrical circuit.... which I assume to be correct whether that circuit is physically connected to earth or is a floating ground situation, and not connected to earth, but serves the same purpose of a return path.....Benny

[Frederick L. Simson]

I keep hearing this, so I must ask the questions.
What is ground?
How does ground (electrical) relate to a fiberglass trailer?

I have experienced this when initially installing "other-than-4-pin-flat" connectors on tow vehicles. In a standard "4-pin-flat" harness of the "plug-and-play" variety, the white "ground" wire comes from the ground circuit path already in the wiring harness. In the adapter recepticles for 5, 6, and 7 pin round arrangements, the white wire from the 4-pin-flat input [b]is not connected! They expect you to find a separate frame grounding point near the mounting location of the round recepticle! I would always experience Kevin A's symptoms until I would splice in a ground connection back to the original 4-pin-flat wiring harness' ground wire! They assume that the frame is ground, but it is not always the same ground as the original harness ground.

[Suz]

I'm sure you've done this, but if one bulb is brighter than the other, the first thing that I would do is make sure they are the same size bulbs. When doing so, make sure that they are the correct bulb (i.e., two filament). If you haven't checked that, I'd certainly start there. If they appear to be correct, then swap sides with the bulbs and see what happens.

Next part I'm a little confused on. You said they are on all the time, but then they don't light up? Do you mean it is like when you have your headlights on and they stay on, but get brighter when you put your foot on the brake?

I recently had some light malfunctions on a trip. First thing I did was to check my bulbs. Then I started checking for a bad ground. Thought I found it, but that wasn't it. I then had a clue as to the culprit, but it didn't seem to be it so I started tearing into the wiring on the inside. Long story short my instinct was correct, it's just that I had not verified it correctly the first time.

Although it wasn't the same problem as yours, I can tell you that I found that it is usually something very simple and I'd sure start with those things before I started tearing into the trailer like I did.

[Suz]

What I can't seem to understand is why there would be any lights at all if there was a bad ground. I don't really understand this stuff all that well, but I thought that if you had no ground, then you'd have no lights at all. Like when the lights flicker, you could have a loose wire or loose ground. Like I said, I don't know much so I'm really asking and not telling.

I kept thinking about the grounding issue on mine, but I had one tail light that worked perfectly, but no running lights or right rear light.

Mine was a fuse. Which was also one of the first things I checked. Unfortunately I have two fuses boxes (which I knew) and a poorly laid out owner's manual. It was easier identifying the source that was blowing it, once I had that down.

[Kevin A]

Thanks to everyone for their thoughts thus far. Yes, it's a new bulb and I checked it in the other tail light. It works fine there. The wiring is hooked together to ground and all the other lights work fine. I'll take the housing off later this week and see if there are any metal parts touching that shouldn't, but at first glance I cannot see any.

Kevin

[Byron Kinnaman]

There are only two things. Remember this!!! That can cause electrical problems.

Something is connected where it shouldn't be.

or

Something is not connected where it should be.


There's nothing else period. No matter whether the convention of calling the negative common connection "ground" or not.

The cause of both filiments on when the tail lights are on, something connected that shouldn't be.

If with the tail lights off and the brakes applied no brake lights, something is not connected that should be.

Sounds simple don't it.

[Darwin Maring]

Just add an additional wire from the metal plate on the lite frame to the metal frame of the trailer and that is a ground.

Add an additional ground wire from the Tug to the White wire receptacle and make sure the white wire on the trailer plug is attached to the frame of the trailer. Both must be connected to bare metal on both the tug and egg frames.

The last ground: Put a ground strap on the tong of the trailer with an alagator clip on the other end and attach the clip to the Tug trailer hitch where it will make contact with bare metal. I use a clip from an old set of jumper cable.

Now, that is total grounding.

You can not rely on the trailer tong hitch making contact with the ball for a good ground.

[Gina D.]

I actually had a similar problem with one of my Pop Ups.

The trailer lights all worked as they should have for months.. then, one trip out.. turn on the running lights and turns and brakes didn't work anymore. Nothing had been rewired. No changes were ever made. It wasn't broke, I didn't fix it.

Took it to a friend that does auto electric. He immediately checked all the grounds.. finding a corroded crimp in the lug that connected directly to the trailer frame. Replaced crimp and lug with solder and shrink tube, new lug, reconnect.. all worked well.

There was a weak connection, so it passed continuity.. but .. lots of corrosion makes things squirelly.

[Brian B-P]

The white wire of my 4-to-7-pin adapter was deliberately not connected to the white (ground) pin of the 4-pin, because that ground wire may be of inadequate size to service the charge and brake lines. The 7-pin connector's 10-gauge white wire was separate, and I connected it to a wire I ran direct to the battery negative terminal. I also tied it to the hitch receiver as a frame ground, but the frame is not required to provide a return path for any circuit to the trailer.

If only lighting was to be operated, then using the ground of the 4-pin connector would work, but it would not be adequate for my application, which includes brakes and charging.

[Brian B-P]

I had a somewhat similar problem with a car's headlights. In both a high-low headlight and the usual two-filament stop/turn/tail bulb, there are two filaments inside the bulb, each having their own connection plus sharing one more connection. Interesting circuits can be made of this.

In my Boler tail lights (and presumably in Kevin's Burro), the shared connection is the "ground" (white wire) - that's the wall of the socket (or shell of the bulb base). The two contacts on the bottom are for the two filaments. In my car, the common connection was broken, and when one filament was supposed to be on, power flowed through the filament which was supposed to be on, then "the other way" through the one which was supposed to be off, across to the light on the other side of the vehicle, through the other one which was supposed to be off, then back to "ground" there.

This drawing shows two bulbs, their corresponding contacts connected together, a bad ground on the left bulb, and two paths for power when only one is supposed to be on: one path (shown in green) lights up the intended filament of the right bulb, the other (shown in red) goes through all the other filaments, lighting them up dimly (because they are in series). This is what happened with my headlights, and shows a possible way to have light in a bulb with no ground connection. Maybe nothing to do with Kevin's tail lights, but maybe a possibility to consider.




Edit note: I realized that the wiring above was for my headlights (as I mentioned) but the bulbs looked like tail lights (which have only one common circuit, not two), so I clarified the drawing.

[Brian B-P]

When I removed my left Boler tail light for cleaning and re-sealing, I messed up the ground and the lights behaved erratically. I didn't trace down the power flow as I did with the car headlight situation, but it can be similar.

Here are a few versions of my previous drawing, but for tail lights (wired with combined brake/turn signals, separate left and right), in a few conditions. In each case, green lines are intended power flow, and red power going where it shouldn't. As I said, some weird effects can result from a bad ground...


[attachment=4387:attachm
ent]



I hope this is helpful, or just amusing; any way, drawing it is one way to think systematically through the situation.

[Joe MacDonald]

good work Brian, I was thinking along those lines myself, have been a victim of bad ground before.

[Dan M.]

In more years as an electrician than I care to admit, I would check the simple things first.

Grounding won't usually give a light brighter than normal. Dimmer, flickering non- existant but rarely brighter.

The first thing Iwould check is if the lamp is in the right direction. Brake / Tail light lamps have pins at different heights which are not readilly apparent. The lamp can easilly be inserted 180 degrees out and then rotated with just a more effort. The effect would give that tail light bright all the time and the brake light barely enough to see through the other light.

Sorry if someone already replied on this, but I have seen a lot of cars going down the road wirh one tail light brighter than the other.

[Lee Hillsgrove]

Sorry if someone already replied on this, but I have seen a lot of cars going down the road wirh one tail light brighter than the other.

Those may have been rear facing fog lights - common on European cars. They work very well when people use them as they are intended, but are rather annoying when they are not - kind of like forward facing fog lights.