# Tail Light



## Golden Mom (Apr 25, 2004)

Hi! Our tail light went out this past weekend. We changed the bulb but it still doesn't work. Any suggestions?

Thanks! sunny


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## Reverie (Aug 9, 2004)

This process assumes the following:

1. The trailer is electrically connected to the tow vehicle.
2. The lighting on the tow vehicle works properly (all lights are appropriately lit).
3. Only one light is malfunctioning on the trailer.
a. If all the lights are malfunctioning, proceed to step 4.
b. If the tow vehicle lights are not operating properly and the corresponding light on the trailer is not operating properly, you most likely have a malfunction of the tow vehicle lighting system.
4. You have attempted to replace the possibly malfunctioning bulb.
a. If is the correct bulb.
b. The bulb is properly inserted and installed.

(NOTE: It is often useful to swap the bulb between two similar lights to see if the bulb is actually bad. Often this reveals bad replacement bulbs).

1. Remove the new bulb and examine it. Does the filiment appear intact? If not, try another bulb.

2. Examine the connectors on the bulb. Are the corroded? If so, remove the corrosion with a piece of emery paper and try the bulb again. Does it work?

3. Examine the bulb connector. Is it corroded? If so, disconnect the electrical connector from the tow vehicle and remove the corrosion with a piece of emery paper. Reinsert the bulb and reconnect the electrical connector to the tow vehicle. Does it work? If not, go to next step.

4. Remove the electrical connector from the tow vehicle. Examine the connector. Is it damaged? If so, has the damage impacted the electrical connectors? If so have it repaired if not go to next step.

5. Examine the electrical connector on the tow vehicle. Is it damaged? Are all seven (7) pins in place? If not, have it repaired, if so go to next step.

6. Examine the back of the electrical connector on the tow vehicle. Is it damaged? Do all the wires appear intact? If not, have it repaired, if so proceed to the next step.

If these steps do not solve the problem you will need an electrical diagram and a voltmeter to proceed. If you do not feel comfortable with using these tools you need to consult a professional.

Reverie


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## tdvffjohn (Mar 10, 2005)

Wow Reverie. I thought I was reading a Chilton Manual. Nice job


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## Reverie (Aug 9, 2004)

Thanks. I'm a retired Avionics technician for the USAF and taught Avionics for four years. I also spent four years as a Technical Writer. What this has created is a know-it-all GEEK.

Reverie


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## Ghosty (Jan 17, 2005)

Reverie

damn -- if you only did taxes too !!!!









Great job... my answer was going to be simply not use your brakes or turn on your lights and you would never know it wasn't working -- but your solution seems slighly better....


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## cookie9933 (Feb 26, 2005)

The way to trouble shoot these things is to use a test light or a digital volt meter. An inexpensive but adequate digital voltmeter can be had for around $20. A quality test light will set you back $6-$8. Before you do anything, prove that you have a good taillight bulb by powering it and seeing it light up. Power it right from the TVs battery with short jumper wires. A broken filament is sometimes hard to see and it is possible that a brand-new bulb won't work. See the bulb light up. Then, go to the plug at the TVs back bumper. Be sure all contact points in the both TV and TT connectors are clean and without corrosion. Then use the test light or voltmeter probe to be sure you have power at the appropriate terminal in the TV plug. If you do, plug in the TT and go to the inoperative light on the trailer. If you don't have power at the "appropriate terminal", repair the appropriate wire on the TV. Now check that you have power at that TT bulb socket and that it is also clean and not corroded. The bulb must be held tightly in its socket for a good connection. If you have power there the bulb should be lit. Note: when checking for power, make sure you are getting ground from the bulb's socket. This will demonstrate that you have both power and ground at the socket.

It's not that difficult to identify where a problem is schematically if you separate the circuit into TV and TT sections. Rule out as many things as you can, one at a time, and as you narrow down the possibilities the process will point at the problem. Rule out the simple things first. For example, be sure the bulb works, be sure there is power at the TV plug, etc. Don't assume that anything is OK unless you prove that it is. However, if you deduce that a certain wire isn't bringing power to where it's supposed to, it can be time-consuming to find the exact location of the problem, such as in the underbelly where wiring is not very accessible.

One thing to keep in mind is that usually there is only one cause for the inoperative light. It is very unlikely that you have two or more problems occuring simultaneously that are responsible. That fact makes it easier to sort it through. But always break things down into simple checks to rule out possible causes one at a time. The answer to the problem will probably be found fairly easily and corrected easily too.

Bill


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## CamperAndy (Aug 26, 2004)

Golden Mom said:


> Hi! Our tail light went out this past weekend. We changed the bulb but it still doesn't work. Any suggestions?
> 
> Thanks! sunny
> [snapback]44266[/snapback]​


When you say tail light do you just mean one of them or all of them?? It can make the troubleshooting window much narrower.

Using the diagram below put a jumper fuse between terminals 3 and 4 on the trailer plug. use a 20 amp in-line fuse and this will light up all your running and tail lights. If it pops the fuse you have a short that needs to be fixed. You can then go around and check all your lights and check for voltages.

BTW - you can do the same thing by connecting up your TV to the trailer and turning on the lights but this is part of the divide and conquer methoh of troubleshooting.


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## Golden Mom (Apr 25, 2004)

CA: It's just one light. The right one. We noticed some corosion on the bulb itself, so DH says he will look at the inner workings as well. He doesn't have time to do much posting so I posted this for him. I appreciate all of your replies and will forward on to him, as this "process" is way over my head. I know nothing about "electrical stuff". I just know the light doesn't work!


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## California Jim (Dec 11, 2003)

Hey CA: What does the center "Auxillary Orange" run ??


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## tdvffjohn (Mar 10, 2005)

Aux. I use it for back up lights on the trailer

John


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## Reverie (Aug 9, 2004)

This is Outbackers.com. Getting a question answered is a little like trying to sip water from a fire hydrant. Jane Wyman, Ronald Regan's first wife, said of him that you ask him for the time of day and he tells you how to build a watch. Well, there we go again...

Reverie


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## cookie9933 (Feb 26, 2005)

Beth,

Ok, you say the right light doesn't work. That's the tail light, correct? The light that is on whenever your TV's headlights are on? (In other words, NOT the right brake light). If that is the case, the problem is definitely somewhere on the trailer. The brown wire in CamperAndy's picture powers both tail lights as well as all marker lights on the trailer. Note: by the time the brown wire gets to the tail light it is black, but that is not the same as wire #4 in the trailer plug. THAT black wire is connected to the positive side of the TV's battery, possibly through the ignition switch. The "brown" wire, even if it is a DIFFERENT COLOR at the tail light is switched through the headlight switch on your TV's dashboard. If only the right tail light is inoperative there are three general possibilities, or combinations thereof: 
1. Power isn't getting to the the light socket by way of the the brown wire, or 
2. The bulb is bad. Hopefully, you have already ruled #2 out. Or, 
3. The socket that holds the bulb has a problem.
Although I said it would be very unusual to have two separate problems occurring simultaneously, it is possible. Being methodical in troubleshooting will allow even multiple problems to be identified.

For #1, the brown wire splits to go to both tail lights and to all marker lights. Somewhere a connection came apart, probably between the two tail lights.

For #2, self explanatory.

For #3, understand that the metal part of the socket itself must be grounded to the negative side of the battery via the white wire. Although you don't see the white wire when you remove the trailer's tail/brake light lens, it is riveted to the back of the metal plate that is common with the socket. Remove the one phillips screw and slide the metal plate sideways to see that the riveted connection is intact. The socket must hold the bulb tightly enough that electrical continuity is assured. Also, be sure there is no corrosion. Inspect the two contacts at the bottom of the socket making sure that they are firmly touching the contacts on the bulb. The 1157 bulb has two separate filaments, the dimmer one is for the tail light and the brighter one is for the brake light.

If the inoperative filament is for the right brake light rather than the tail light, the same things apply except you will be looking for a bad connection somewhere along the green wire. But it is possible that the problem is on the TV with this one. Be sure that power comes from the green wire at the trailer plug when the TV's brakes are applied. If it does, the problem's with the trailer. (Confused yet?) On the trailer, since the green wire does not split to feed any other bulbs, there are less potential connections to fail.

If you have a short anywhere, one or more fuses should be blown. If there are no bad fuses, a short is very unlikely. (Don't want to confuse you by mentioning dead shorts versus partial shorts or intermittent shorts for that matter)









I know that for some folks, the operation of a flashlight is mysterious. But most people understand the concept of a DC circuit, which is very simple. Even though vehicles and trailers have a lot of wires and connections on those wires, the principle remains simple. If my explanation is overly simplistic, I apologise. If it is too complex, ask further questions and myself or someone else will probably be able to explain things better.

Bill


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## cookie9933 (Feb 26, 2005)

John,

You is the MAN! Having backup lights on the trailer so you can back into your campsite in the dead of night. Until now, it's been enough for me to do it in broad daylight. But that's gonna change: flamethrower backup lights are going on the Outback.









Bill


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## cookie9933 (Feb 26, 2005)

Golden Mom said:


> CA: It's just one light. The right one. We noticed some corosion on the bulb itself, so DH says he will look at the inner workings as well. He doesn't have time to do much posting so I posted this for him. I appreciate all of your replies and will forward on to him, as this "process" is way over my head. I know nothing about "electrical stuff". I just know the light doesn't work!
> 
> 
> 
> ...


 action Hi Golden MOM,
The Geek Guys on Outbackers could write a tech manual on Outbacks. I know they could build them better then the Keystone "techies"








I agree with you I read this stuff and its over my head too! shy 
I guess we better stick to sheets and shopping








Jan just wants to have fun


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## Katrina (Dec 16, 2004)

California Jim said:


> Hey CA: What does the center "Auxillary Orange" run ??
> 
> 
> 
> ...


CJ, The center pin, while labeled as AUX, should already be wired as back up lights on your burb. Thats the way GM does it if you have the factory 7 pin plug.


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## CamperAndy (Aug 26, 2004)

California Jim said:


> Hey CA: What does the center "Auxillary Orange" run ??
> 
> 
> 
> ...


Standard new wiring is to the back up lights but when the 7 pin standard was set they left it up to the user. The only other light I could guess that it would be connected to would be your truck bed light switch. Say if you had a close snow mobile trailer and it had lights they could be wired to this as an example.


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## Katrina (Dec 16, 2004)

CamperAndy said:


> California Jim said:
> 
> 
> > Hey CA:Â What does the center "Auxillary Orange" run ??Â
> ...


It is commonly used for interior lights on horse trailers around here.
but with horses around these parts selling for upwards of 4 million, I guess they deserve a "night light"


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## summergames84 (Mar 6, 2004)

Golden Mom:
We had a similar problem but with the left tail light. We sprayed some WD40 on the 7 pin connector and it solved the problem. I do not know why. I'm sure Reverie can give us the scientific numbers of all the ingredients in the WD 40 that made this work.


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## Firefighter2104 (Apr 25, 2004)

OK Golden Mom has me working in the rain from Dennis and I got it working half way.









I tired the simple way 1st and cleaned off the socket and the brake light starting working. The turn signal is still out. I liked the 10 W40 idea that seam to always work.

I do have one question when I bought the new bulb the guy gave me a 1157 and while I was working in the rain I noticed that the plate of the light says to use a 1156 bulb. Does anyone know what the difference is if any?

Thanks for all of the ideas.

Bill


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## CamperAndy (Aug 26, 2004)

1156 is a single element and the 1157 is a double element bulb I will need to look to see if they have different pin locations.

On edit - Okay I looked it up the 1156 has a single contact base and the 1157 has a two contact base, I should have know this from the fact that the bulbs have different numbers of elements.


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## cookie9933 (Feb 26, 2005)

Just for grins and also because we will be leaving on a somwhat long trip, I wanted to know what bulb is used so I can take several spares. Popped a lens off and saw one 1157 bulb. The plastic base of the light assembly says "1157 bulb" at the bottom half of the space and also says "1156 bulb" at the top half. The top half could carry a 1156 bulb for backup lights if there was a second socket, but the second socket is not there. In other words, that base can be built with or without a backup light. Look at it again and you will see what I'm talking about. You failed to see the words "1157 bulb" in the lower half.

You mentioned that the turn signal isn't working either, although the brake light now is working. Please understand that the brighter filament in the bulb is for both brake lights and turn signals. The dimmer filament is for the tail lights only (also could be called running lights). Since you say that the turn signal still doesn't work, I must assume that the tail light filament is working. But, is that tail light perhaps dimmer than the other side? If it is, I bet you have a ground problem with the socket for that bulb. With a poor or non-existant ground, a bulb can work dimly because it gets some grounding via feedback through another bulb that's in parallel on the circuit. Also, do you know whether you are getting power through the green wire? You need to be checking the white ground wire that's riveted to the back of the metal plate (already mentioned) as well as the green brake/turn signal wire. But, I suspect it's poor or no ground. Let us know.

Bill


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## Firefighter2104 (Apr 25, 2004)

OK I re-looked at the bulb # and see I the 1157 on the bottom half, so I do have the right one. The light is very bright both with the left turn signal and the marker light. I have even taken the bulb out of the other side and it works fine, so it's not the bulb. When I turn on the Left signal the right side does dim or has a slight blink to it.

I have took and ran a ground wire to another ground with no luck. I have checked the white ground wire and it looks ok.

If I run a meter to that socket what should I get, so I know it's working.

Any other ideas???









All of the other lights are very brght.

Bill (cookie9933), are you saying that the brake light and the Trun signal are the same filament and the other one is marker light? If that's the case why would it be lit up when only the marker lights are in use?


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## cookie9933 (Feb 26, 2005)

Bill, 
Since we are leaving on a trip early Friday morning, I may not be able to see you through to success. I'm sure others will help if necessary.

You say that when you put on the left turn signal, the right bulb goes dim or has a slight blink. In my experience, this indicates a poor ground somewhere. Hopefully, the trailer's metal frame is connected to the white wire that comes through the triler plug. When you said you used a piece of wire to ground the right bulb socket, did you get your ground from the trailer's frame? Do this again but go to both rear lights, left and right. See if that test fixes the problem. If it does, you will need to repair or replace the offending ground wire. If it doesn't cure things, you will have to do different voltage checks on the wires that should be bringing power to the bulbs. You want to have close to 12 volts from those wires when they are switched on. You want to read close to zero when they are off. A digital voltmeter can read very small stray currents sometimes. That's why I said close to zero. It will be OK if you read a few hundredths of a volt.

And yes, absolutely, the turn signal and the brake light are both on the green wire that operates the bright filament in the bulb. The other (not as bright) filament is only for the tail lights, which are sometimes called running lights or marker lights. If the left side is working correctly, you will see that to be the case.

If you have the running lights on and apply the brakes, both filaments will be lit.

If you operate brakes and turn signals at the same time while running lights are off, the bright filament will blink and the dim filament will be off.

If you have marker lights on and apply brakes and use the turn signals at the same time, the dim filament will be on and the bright filament will blink.

If you have running lights on and you operate the turn signal without brakes, the dim filament will be on and the bright one will blink.

Etcetera. That's all I have time for right now. Gotta get to bed. Good luck finding the problem.

Bill


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## Firefighter2104 (Apr 25, 2004)

DONE

I found the problem!! I tested the plug on the truck and found I wasn't getting power to it. I found a 10amp fuse blown in the side fuse box under trailer wring.

Thanks for everyone ideas!









Bill


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