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chrisallenhogs

Question about vehichle plug for trailer lights

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chrisallenhogs

I have a 2004 Chevy Silveraldo and brand new boat trailer. I can't seem to get the night time lights to run. The blinkers and brake lights work. I have a 5 prong trailer wire harness. Does anyone else have this problem. I checked all the fuses and nothing was wrong. I also checked the adapter and all seems to be wired correctly. My old boat did this as well, however I thought it was due to the trailer being messed up. Any ideas?

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SFD
I have a 2004 Chevy Silveraldo and brand new boat trailer. I can't seem to get the night time lights to run. The blinkers and brake lights work. I have a 5 prong trailer wire harness. Does anyone else have this problem. I checked all the fuses and nothing was wrong. I also checked the adapter and all seems to be wired correctly. My old boat did this as well, however I thought it was due to the trailer being messed up. Any ideas?

Take it to any trailer place - they should have the plug in tester that identifies what is wrong.

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BillFooter

Or you could check the plug on the truck with a test light to see if the prongs that operate the running lights have power.

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chrisallenhogs

Which hole is for the running lights?

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BillFooter

Stole this off of a triler parts website.

Trailer wiring and harness plugs are available in a variety of sizes and configurations. The most basic of designs is the color coded 4-WIRE system which uses a brown wire for tail, license, and side marker lights, yellow wire for left hand stop and turn, green wire for right hand stop and turn, and white wire for system ground. The "Flat-4" harness plug is found on almost all boat trailers and many smaller utility trailers that do not have brakes.

5-WIRE systems provide all the color coded functions of the 4-pole systems plus an additional blue wire which may be used for Hydraulic disc brakes or auxiliary lights.

post-89-1210726788_thumb.jpg

Edited by BillFooter

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ucontrol
I have a 2004 Chevy Silveraldo and brand new boat trailer. I can't seem to get the night time lights to run. The blinkers and brake lights work. I have a 5 prong trailer wire harness. Does anyone else have this problem. I checked all the fuses and nothing was wrong. I also checked the adapter and all seems to be wired correctly. My old boat did this as well, however I thought it was due to the trailer being messed up. Any ideas?

Unless your vehicle has been altered, the lights are pre-wired from the factory. Next to the hitch receiver, there is a large round plug with a cover over it. You should have recieved an adapter with the vehicle. If not, then you can buy one at any auto parts store , RV dealership or chevy dealer. IF your boat has disc brakes, then you will need to buy a 5 way plug. With disc brakes, you cannot backup the trailer without the back up wire connected. The brakes will lock up in reverse without the 5th wire.The plug adaptor you will buy uses the center prong for this application and should be already in place on your vehicle from the factory. The running lights, tail, uses usually a brown wire. If you do not have disc brakes on your trailer, then a 4 way plug will work. If you happen to buy a 5 way plug and you do not need the 5th wire, Backup, then you simply move the boat wire down in the vehicle plug to bypass the backup wire. In other words if you only need 4 wires, you can skip the 5th wire. Of course this is all based on your boat being wired the same as the pre- wired chevy vehicle.

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chrisallenhogs

The truck is pre wired and I do have the adapter, I have a dorsey tandem axle trailer with disc brake so I need the 5th wire. I'm not very good with this kind of thing and have checked all the fuses and seems to be fine. I assume it is not the trailer becaue it is brand new. I will see if I can check the brown wire. I might just need a new 7/5 adapter.

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FijiRob

I had a similar issue a few years ago with my Dorsey trailer. IIRC one of the trailer bulbs was loose which ended up shorting the entire trailer for some reason. Try checking each bulb to make sure it has good contact. Hopefully it will be a quick fix.

Rob

Edited by FijiRob

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D-GOOSE

Recheck the truck fuse's. You will have a truck running light fuse AND a trailer running light fuse.

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MalibuTime

After checking the above suggestions, then...

First, you may not have a good ground from the truck to the trailer. With the boat trailer hooked up, and the plug in, jump a wire from a bare metal spot on the trailer to a bare metal spot on the truck and check them. Had this problem this weekend ( as a side - not sure exactly why the plug ground was not grounding, but once the rust wore off the ball it grounded there). If this test fails, then you know it is not a simple grounding problem, which is often the problem with trailer lights.

Second, you can also check the trailer lights by themselves. Use a 12 volt power source, or even a lantern battery (big flashlight battery - 6v or whatever) to see if your trailer circuits are lighting up. Battery ground to trailer ground - white wire, the only prong on the trailer side, or to a bare spot on the trailer, and positive jumped to each of the remaining 4 trailer wires to see if the respective lights light up. Technically, the hot wire should probably be fused, but some people would skip it Whistling.gif and just see if the dang lights lit up.

If this test fails, then something is up with the trailer wiring. (not to rule out something could still be wrong with the truck wiring though)

Edited by TheBlackPearl

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chrisallenhogs

Does anyone knwo what Chevy calls the running trailer light fuse? I don't see it the manual.

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EZSnow

If your stop/turn lights are working without incident, then *most likely* the ground is okay. At any rate, it is functioning well-enough that it shouldn't prevent the running lights from working.

On a flat-four or flat-five, on the truck side plug, the ground is the exposed pin, running lights are the socket that is closest to the ground pin. Get a test light at a hardware/auto parts store. (a cheapie shouldn't be more than a few bucks, and every trailer owner should have one) Turn on the parking lights on the truck, then clip the alligator clip of the test light on the ground pin for the truck. Now stick the probe inside the previously described running light socket, being careful to ensure that the probe is making contact with the metal sleeve around the outside of the socket. If the truck is functioning properly, the test light will light, and the trailer is likely to blame.

If the test light does not illuminate, there is a problem on the truck side. Leave the clamp on the ground pin, and turn the 4-ways on the truck on. Now probe the next two sockets in line, and on each one you should get a flashing test light. The flashing test light verifies that the stop/turn circuits are working, and the ground is working. At this point, you most likely have a blown fuse on the truck. It is possible, but highly unlikely that the harness is chafed or somehow broken. Your truck *should* have a separate fuse for just the trailer parking/running lights. On my '99 silverado and 2000 suburban, it was in the underhood fuse box. It is likely marked "trailer park" or "trlr prk"

If the truck checks out, and NONE of the running lights are working on the trailer, you most likely have a broken wire near the front of the trailer, before it splits down the two sides.

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skicrave

Great post EZ!

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NorthernDancer

First thing, I would go to your power control box in the front engine compartment of the truck and locate the trlr fuses. There are two as I recall. The running light one 10 amp is likely blown. Any ground fault or short will blow it. You probably did that with your old trailer and never would have known as the circuit only runs the running lights on a trailer.

If that fuse is OK, then start troubleshooting at the plug end and trailer as the others have suggested.

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ucontrol
The truck is pre wired and I do have the adapter, I have a dorsey tandem axle trailer with disc brake so I need the 5th wire. I'm not very good with this kind of thing and have checked all the fuses and seems to be fine. I assume it is not the trailer becaue it is brand new. I will see if I can check the brown wire. I might just need a new 7/5 adapter.

Under the hood in the front of the vehicle, there is another set of fuses that also control the main lights. But, if this fuse is blown, then your main lights on the vehicle will be not working even when the trailer is not plugged into it. So check the lights on the truck to make sure they are still working without the traller. I am assuming you are using the normal flat plug on your trailer? Some of them are round. But the info I gave you is based on the flat 4 or 5 way flat plug which is how the chevy setup is wired. Good luck

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EZSnow

Since the '99 body style, all GM trucks with a hitch are 7-way round with RV (flat) pins from the factory. You need an adapter to get to a flat-4 or flat-5. Or, you re-wire the boat with a 7-way and be done with it...

To add to the above, the wire colors are easier to remember than you think, and are as follows:

White- Ground, negative

brown- running lights

yellow- Left stop/turn (notice, "yellow" has an "L" in it for "Left")

green- Right stop/turn (notice "green" has an "R" in it for "Right")

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electricjohn

And blue- Reverse lights, also used for the backing solinoid on trailers with surge brakes. Chances are your truck might need a trailering relay. This isolates the trailer wiring from the trucks wiring, so faulty trailer wiring won't damage your trucks wiring. The tow option usually includes the installed relay. If you don't have the tow option, you have to buy and install the relay.

Edited by electricjohn

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MalibuTime
If your stop/turn lights are working without incident, then *most likely* the ground is okay. At any rate, it is functioning well-enough that it shouldn't prevent the running lights from working.

:Doh:

Totally spaced the original post in my reply. THX for setting that straight!

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hattric73

Just to add to the confusion...I believe there are two methods to wiring RV plugs. I don't know the name of either but they both fit into the 7 pin socket but the wires are in different places. I know we have an adapter in our truck in case we need to pull a trailer that is wired in the other method.

Sorry, not that much help but, like others have said, see if a trailer/truck supply store can help you out!

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EZSnow
Just to add to the confusion...I believe there are two methods to wiring RV plugs. I don't know the name of either but they both fit into the 7 pin socket but the wires are in different places. I know we have an adapter in our truck in case we need to pull a trailer that is wired in the other method.

Sorry, not that much help but, like others have said, see if a trailer/truck supply store can help you out!

There are two ways to wire a six-way round... Normal, and cowboy. I don't pull much six-round, so I don't even have an adapter, but the discrepancy comes between the constant (+) and the electric trailer brake (+). In one configuration they are opposite of the other, so if you have the wrong adapter, as soon as you plug in to a trailer with electric brakes, the brakes lock and you can't go anywhere. Most of the seven-way to six-way adapters (all that I have ever seen) can be opened and there are two wires that can be switched back and forth to change configurations. This, along with a phillips screwdriver will allow a guy to pull a six-way of either configuration. This really doesn't come in to play on our boat trailers, as they do not use constant (+) or electric brake, but disc brake trailers require a (+) signal while in reverse to lock out the brakes, which a six-way does not provide.

I use a switch to activate the reverse light (brake lockout) circuit on my truck, so I can lock the brakes out at will- either coasting down a hill to avoid overheating trailer brakes, or if you get in a situation where the trailer brakes are applied before the truck is put in reverse, then you can't back up... I just flip the switch while I'm pulling forward, then stop and back up- works like a champ!

There are two types of seven-way round connectors, but they are not at all cross-compatible. One is the standard 7 flat terminals arranged in a circle (well, six-and-one) which is the one used on light trucks- commonly called "7-way RV". The other is the one used on big rigs- it has a similar size and layout, but uses round pins instead of flat. I have no idea what the standard pinout is on them, or what they are "called" but they are usually only see on semis and big dump trucks.

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hattric73
Just to add to the confusion...I believe there are two methods to wiring RV plugs. I don't know the name of either but they both fit into the 7 pin socket but the wires are in different places. I know we have an adapter in our truck in case we need to pull a trailer that is wired in the other method.

Sorry, not that much help but, like others have said, see if a trailer/truck supply store can help you out!

There are two ways to wire a six-way round... Normal, and cowboy. I don't pull much six-round, so I don't even have an adapter, but the discrepancy comes between the constant (+) and the electric trailer brake (+). In one configuration they are opposite of the other, so if you have the wrong adapter, as soon as you plug in to a trailer with electric brakes, the brakes lock and you can't go anywhere. Most of the seven-way to six-way adapters (all that I have ever seen) can be opened and there are two wires that can be switched back and forth to change configurations. This, along with a phillips screwdriver will allow a guy to pull a six-way of either configuration. This really doesn't come in to play on our boat trailers, as they do not use constant (+) or electric brake, but disc brake trailers require a (+) signal while in reverse to lock out the brakes, which a six-way does not provide.

I use a switch to activate the reverse light (brake lockout) circuit on my truck, so I can lock the brakes out at will- either coasting down a hill to avoid overheating trailer brakes, or if you get in a situation where the trailer brakes are applied before the truck is put in reverse, then you can't back up... I just flip the switch while I'm pulling forward, then stop and back up- works like a champ!

There are two types of seven-way round connectors, but they are not at all cross-compatible. One is the standard 7 flat terminals arranged in a circle (well, six-and-one) which is the one used on light trucks- commonly called "7-way RV". The other is the one used on big rigs- it has a similar size and layout, but uses round pins instead of flat. I have no idea what the standard pinout is on them, or what they are "called" but they are usually only see on semis and big dump trucks.

Thanks for the correction! My bad!

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