Trailer Running Lights Not Working
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Trailer Running Lights Not Working
Hello everyone. im new to the site and have a question my truck is a E99 7.3L f350. I can not get running lights to work on my 5th wheel. I have checked the following i have hooked the camper to another power source and all the lights work. i have checked the power coming out of the 7 pin connector with no power coming out, i have checked/changed the fuse under the hood and still nothing, I was told the relay under the radio controlled the marker lights so i changed both of them and still no luck, i made a new ground and still no lights. im not the smartest man by no means but i feel as i have checked everything i know to check. am i missing anything or can someone point me in a further direction? also whats your thoughts on running a new light wire from the tag light to the 7 pin connector? all brake lights and turn signals work on the trailer when hooked to the truck but no running/marker lights. Thank You All so much for the help
Logistics Pro
Joined: Aug 2009
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From: Arizona
Are you using the 7 pin connector on the bumper or did someone add one to the bed? On my truck they added one to the bed and did a horrible job of tapping into the original harness and needless to say I had issues. I bought a new harness and 7 pin connector assembly off Amazon to install, (plug & play)
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Are you using the 7 pin connector on the bumper or did someone add one to the bed? On my truck they added one to the bed and did a horrible job of tapping into the original harness and needless to say I had issues. I bought a new harness and 7 pin connector assembly off Amazon to install, (plug & play)
Logistics Pro
Joined: Aug 2009
Posts: 3,609
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From: Arizona
If the truck's running lights work I would assume a bad connection where you plugged things together or upstream of there. In other words, the lights on the truck work so that confirms the fuse is good so it has to be a bad connection or broken wire somewhere. To my knowledge the 7 pin is not fused separately from the truck's lights. The fact that the brake/signal lights on the trailer still work confirms the ground is good. So with the fuse good and the ground good it can only be an open circuit somewhere on the running light circuit. Maybe disconnect the Etrailer jumper and check for power from the truck at that point with a 12 volt test lamp and probe. Make sure none of the terminal pins got bent or pushed back out of the plastic housing.The problem is most likely where the most recent work was done.
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If the truck's running lights work I would assume a bad connection where you plugged things together or upstream of there. In other words, the lights on the truck work so that confirms the fuse is good so it has to be a bad connection or broken wire somewhere. To my knowledge the 7 pin is not fused separately from the truck's lights. The fact that the brake/signal lights on the trailer still work confirms the ground is good. So with the fuse good and the ground good it can only be an open circuit somewhere on the running light circuit. Maybe disconnect the Etrailer jumper and check for power from the truck at that point with a 12 volt test lamp and probe. Make sure none of the terminal pins got bent or pushed back out of the plastic housing.The problem is most likely where the most recent work was done.
the 7 pin connector trailer marker lights is fused separate on a 99 its fuse 4 under the hood. i have disconnected everything and checked the plug attached to the factory harness and im not getting any power. i agree with the brake lights working means the ground is good. i didnt know if im missing a relay somewhere. I think im just going to run a new wire and tie it in with the tag lights.
Logistics Pro
Joined: Aug 2009
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From: Arizona
I didn't know there was s separate fuse but it makes sense. Hopefully someone that knows the circuit for the 7 pin will be around soon. If you tag onto the truck running lights just be sure you are not going to over load that circuit. Did you happen to see if there is running light power at the 4 pin connector?
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yes sir i did check the 4 pin connector and no power ether. if i put an add a fuse in the circuit on switch power than it should be okay versus just splicing a line I THINK
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Logistics Pro
Joined: Oct 2011
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From: Mcdonough, GA
If you can wait till tomorrow I will have access to wiring diagrams and will post up. Maybe someone else can do it today.
is the fuse tight in its socket?
is the fuse tight in its socket?
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Laughing Gas
Joined: Jun 2018
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From: Idaho
I had the same running light issue with my truck. I had both the plug 'n play connection in my bed and bumper. Turned out to be one of the 7 pin connectors had the pin locking tab in the back break and the pin would push out ever so slightly when connecting the trailer plug. So it wasn't getting a solid connection. Make sure your pins are locking in.
Pin was still visibly there when looking at it, but would push back with pressure applied. Double check that. Since the bed and bumper harness were tied together, neither one would work. I had to purchase a new 7 pin connector and transfer the pins/wires since the pin would never stay in with the tab broken.
Pin was still visibly there when looking at it, but would push back with pressure applied. Double check that. Since the bed and bumper harness were tied together, neither one would work. I had to purchase a new 7 pin connector and transfer the pins/wires since the pin would never stay in with the tab broken.
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That Would be greatly appreciated!!! and yes the fuse is tight in the socket i even wiggled it around to see if i got anything...
i have unplugged the wiring from the 7 pin connector and its not getting power at the truck plug so the pins on the plug shouldn't have an effect
i have unplugged the wiring from the 7 pin connector and its not getting power at the truck plug so the pins on the plug shouldn't have an effect
Cargo Master
Joined: Aug 2003
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From: Eastern Washington
Do all the lights on the truck work? Some of the trailer relays share power with some of the truck lights, so they need to all be working.
Do you have power for the backup lights or have power on the 7 pin when the truck is in reverse? They start at the same circuit (#4) as the parking lights.
If your trailer backup light circuit does not work, check for power on Fuse #4.
If your trailer backup light circuit does work, Check for power to the Trailer running light relay, the green and yellow wire at pin 3. It's probably at the fuse panel under the steering wheel but I'm not sure which relay.
If you jump pin #3 to #5, you should have power on the running light circuit, or blow fuse #4.
I would also look for anywhere someone may have tapped into the wiring (usually around the spare tire) and used substandard practices that may have failed.
Also around the filler neck area in case someone was wiring in a camper.
Do you have power for the backup lights or have power on the 7 pin when the truck is in reverse? They start at the same circuit (#4) as the parking lights.
If your trailer backup light circuit does not work, check for power on Fuse #4.
If your trailer backup light circuit does work, Check for power to the Trailer running light relay, the green and yellow wire at pin 3. It's probably at the fuse panel under the steering wheel but I'm not sure which relay.
If you jump pin #3 to #5, you should have power on the running light circuit, or blow fuse #4.
I would also look for anywhere someone may have tapped into the wiring (usually around the spare tire) and used substandard practices that may have failed.
Also around the filler neck area in case someone was wiring in a camper.
Thread Starter
|
New User
Joined: Jul 2020
Posts: 8
Likes: 0
Do all the lights on the truck work? Some of the trailer relays share power with some of the truck lights, so they need to all be working.
Do you have power for the backup lights or have power on the 7 pin when the truck is in reverse? They start at the same circuit (#4) as the parking lights.
If your trailer backup light circuit does not work, check for power on Fuse #4.
If your trailer backup light circuit does work, Check for power to the Trailer running light relay, the green and yellow wire at pin 3. It's probably at the fuse panel under the steering wheel but I'm not sure which relay.
If you jump pin #3 to #5, you should have power on the running light circuit, or blow fuse #4.
I would also look for anywhere someone may have tapped into the wiring (usually around the spare tire) and used substandard practices that may have failed.
Also around the filler neck area in case someone was wiring in a camper.
Do you have power for the backup lights or have power on the 7 pin when the truck is in reverse? They start at the same circuit (#4) as the parking lights.
If your trailer backup light circuit does not work, check for power on Fuse #4.
If your trailer backup light circuit does work, Check for power to the Trailer running light relay, the green and yellow wire at pin 3. It's probably at the fuse panel under the steering wheel but I'm not sure which relay.
If you jump pin #3 to #5, you should have power on the running light circuit, or blow fuse #4.
I would also look for anywhere someone may have tapped into the wiring (usually around the spare tire) and used substandard practices that may have failed.
Also around the filler neck area in case someone was wiring in a camper.
Logistics Pro
Joined: Oct 2011
Posts: 3,953
Likes: 120
From: Mcdonough, GA
Looks like the brown / white wire leaves the relay and goes straight to the back of the truck. Would be nice if you could find it in the cab and verify if power is coming from the relay.