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| Does anyone have a rear brake light wiring diagram for larger trucks? I have a 92 Kenworth T800 where I had the the bed shorted noticed that all the new lights work except the left hand brake lights. |
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Near-north Ontario, French River | Just the left brake light out, and right side is working? Seperate brake and turn light ?? Should be a easy fix. I assume you have tried a new light? If that didn't fix it, check the ground really well, that is often the problem. If that doesn't solve it just trace the wire from the left side, it should "T" into the harness ( other leg obviously goes to right side light). Are you running an LED light by chance? If so check to see that the wires didn't get reversed at the plug when they shortened you bed. LED's are polarity sensitive so if they wires got reversed the light wont work. |
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| I should have clarified. The frame lights is just your regular old halogen and the one one the bed is led. All the lights work, so its not a ground. Do these trucks have a single or two wires that operate the brake lights, one for the left side and one for the right?
The lights have three wires coming out. A black (backup), a green ( night marker), and a red ( brake and signal.) |
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South Western Ontario, Canada | What kind of lights are these?
Should be only one wire for brake lights to the back of your truck.
Ground, white
Tail/clearance, black
Signal. Red. |
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| Ok I see what you are saying about the white, red, black wires on the led lights on the body. The black, green, red are on the lights on the frame.
Edited by Coastal 8/27/2014 12:13
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Elizabethtown,KY | I'd like to see a pic of the whole truck and bed, is that a local made bed? Why does it only have single wheels in the back? |
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South Western Ontario, Canada | I personally hate grounding to the body. You have pulled the plug on the light not working and check it with a test light or voltmeter?
Is the wire actually hooked up to the other side or just laying there? Give gentle tug. |
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NE SD | Throw the POS's truck taillights AWAY ! You have plenty better ones in box. I assume the ambers in box are turns ? |
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| Red/Green here's the whole truck. The rear is just a tag
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| No, the ambers are stobes for when escorting equipment and sitting on side of the highway. |
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NE SD | Sweet ! I would still toss the truck taillight and use sealed grommet mounted |
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| Ok, here is what I have so far. Coming off the chassis, I have a Green, White, White -GND, Red, Red/White striped, Brown, and Yellow Wires.
Green - Works the right signal and brake. (If I hook the red wire from the tail lights I can get both right and left lights to work when applying the brake. But also the left and right sides will flash when giving a right turn signal.)
White - Works the left signal
White GND- not hooked up
Red- nothing
Red/White - nothing
Brown - tail/marker lights
Yellow- Nothing.
Should the WHITE be working both the Left signal and Brake?
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South Western Ontario, Canada | There is a reason why most trucks and trailers have multiple lights per side. Makes cleaner set up.
Do the truck lights operate correctly?
You might be better off buying a modual from a car/pickup and installing it in your truck......four inputs (left,right,brake and tail) and will operate the lights properly.
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SouthCentral WI | I don't think this will help you much. The normal wiring for the rear of trucks is
Brown = tail lights
Green = right turn
Yellow = left turn
white = ground
The brake lights on a 2 bulb system are fed through the turn signal wires.. green and yellow
On a 4 bulb system (for instance the rear of a trailer) the red wire is the brake and gets attached to the inside right and inside left bulb for brake lights and the green goes to right outside, yellow to left outside
Like I said I don't think this is going to help you, but that is the factory wiring.
Edited by towman2000 8/27/2014 16:55
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| Thanks,
Im thinking that what I was calling a white is just a faded yellow. Is there anything that I could replace/swap from the green wire to the yellow. Relay possibly? |
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Near-north Ontario, French River | towman, there is an alternate wire setup . What you describe is a system that uses the same light( one lamp ) for brake and turn. For those set up with separate( two lamps) brake and turn things could be wired... White - ground, black- clearance, brown clearance,red- stop, green- left turn, yellow- right turn. As well some will have a blue wire that can be used for auxiliary ( often used for a back up light, warning buzzer, etc). Check the firewall(( back side of fuse panel) on the truck, you should find the wire harness coming out and heading back to the rear of the truck. Determine how many wires you have going to the back and go from there.
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SouthCentral WI | Coastal
I'm not quite understanding the question you have. The green and yellow are fed through the turn signal switch, which is how you end up with , (green/right turn, brake on left) or (yellow/left turn, brake on right side) or( the turn signal off position the brake feed goes to both green and yellow) . Basically there are to feeds to the turn signal switch. One from the brake light switch (usually air activated) and one from the flasher. then when you flip the turn signal it sends the feed to the correct wire. Some systems use a relay and of course all feeds are fused.
Clear as mud, Right?
Towman
Thud, I did mention a 4 bulb setup but thought I would keep it a little simpler so I didn't mention dual tailight feeds and backup lights and hazard lights, and and and.
Edited by towman2000 8/27/2014 17:35
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| Towman, I guess what I am asking is.
Is there any switch or relay that could have gone bad, thus not allowing the brake signal to be fed down the yellow wire? The yellow has power only when the turn signal is on. But, not when the brake is press with the turn signal off. Green wire functions as it should. |
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| Hate non-standard color coded wiring. Pick up heavy duty equipment lighting catalog from Grote, D-A, or others, or from a dealer like NAPA. Will list not only equipment options, but lighting requirements, plug/socket lay-out, and color codes. Always carry a ground to each load. Have found that sealed lamps, rubber grommets, di-electric grease, wiring clips, and heat shrink are well worth time and cost. Invest in a multi-meter of good quality and learn to use it. |
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| Reverse the colors on the turn signals, and you would following the approved standard. If everyone would follow the standard. |
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| On our fld120 freightliner, the brake light on the left side will not work unless the turn signal lever is pushed forward just a bit. The switch on the steering column is needing replaced. I don't know if your truck is set up like that, but I fiddled with wiring for quite some time before I figured that little trick out. |
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Near-north Ontario, French River | Coastal, if your truck is wired as Towman says, it could be as simple as a wonky turn signal switch on the steering column. Try wiggling things around, throw the 4 ways on and off a few times and see if things work properly after that. |
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SE MN | I see one epic fail. Here in Minnesota the pig tail ground back to the frame will surely be corroded off by spring. Save yourself some time and string a homerun back to the battery |
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Embarrass WI | I was told to remember wiring color by- g-R-een is Right and ye-LL-ow is Left. |
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| my money, is on a bad turn signal switch |
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SouthCentral WI | I would agree with Thud, peculiarly if you have the old style turn signal stat ( it has the hazard switch that you pull out under the turn lever) I think I have a wiring diagram for the old style to help troubleshoot it. I will have to look.
You could go to the wires at the turn signal and check with a test light and make sure that the front left and rear left wires aren't switched. Does the left FRONT come on with the brake. This would indicate a switched wire (left front and rear)
I should explain that the color codes in this drawing is for the wires exiting the 900. The colors on the wiring at the back of the truck should still follow the color code that I first said.
Towman
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SouthCentral WI | Yup
Towman |
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Near-north Ontario, French River | My bad, you guys are correct. Yellow left, green right |
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| Ok, I disconnected the switch just enough so I could get a test light to each of the terminals. I had power to every thing just as towman's diagram showed. I ran a new ground directly from the - terminal on the battery back to the lights, and that didn't fix the problem. So I think I have rulled out the ground and the turn signal switch. Does anyone have a wire diagram as they come out of the fire wall?
Incase I haven't mentioned it before. I hate Electrical issues. |
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NE SD | have no wire diagrams but a few thoughts. From the cab back the wire needs should be as simple as a 7 wire trailer cord running back there that's ALL
How was the truck built ? If it was built as a tractor it will have trailer wire at back of cab plus wire harness for rear of truck, this is where problems can occur as people use unique methods to achieve their goal of working lights.
Start at rear of truck follow wires and see where they run, and the connections, I think you will find it |
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Truck brake light wiring
