Trailer 4-wire, Brakes Turns Hazards Work, No Running Lights

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KingDarius

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So I am stuck at this point. Can anyone tell me how to troubleshoot this? From what I understand, its the brown wire that carries the running lights (which IS connected to the brown on the harness)

Last night, I re-did the grounds as the old ones were really rusty.

It just seems if all the other indicators work, the runners should work too. Any help appreciated...
 
Have you checked to see if you're getting +12v from the connector at the back of your vehicle? The problem may not be in the trailer wiring but in the way the harness is wired in to your vehicle.
 
JMichael said:
Have you checked to see if you're getting +12v from the connector at the back of your vehicle? The problem may not be in the trailer wiring but in the way the harness is wired in to your vehicle.

Agree.
If anything works, your grounds are good as they all connect to the trailer frame. BTW, that's not the most reliable way to connect grounds. I ran white wires for ground from my plug to every light, but that's another story.
Check for 12V at the truck plug. You should have 12V between the pins that go to the brown and white wires. If you have it there, but neither side, then you have a problem between the plug (brown)and where the two sides connect somewhere in the tongue. You have it on green and yellow because those work, but it may not be on the brown.

At this point, you are time and money ahead by picking up a new wiring harness and pulling through the frame. It sounds like you have a bad connection and the others may not be far behind and you could spend a lot of time running them down. You can get a complete harmess about anywhere for around $12. That's how I would go. I would rather spend my time fishing than fixing electrical stuff.
 
Wow ok, thanks guys.

For the record: the trailer harness is brand new. However, the connector on the truck has seen its day (sometimes I have to pull the plug out just a little bit for the other lights to even work). Maybe its the truck connector that is an issue.

I will use the testing techniques listed below and see if they work.

"I would rather spend my time fishing than fixing electrical stuff." Couldn't agree more....
 
What type of truck?

My chevy has a fuse in the dash for trailor running lights that liked to pop when I had a faulty ground
 
A bad ground will not cause a fuse to pop, as current can not flow without a proper ground. A hot wire touching a grounded frame will blow fuses.
 
Voltage spikes/current overloads/ dead shorts blow fuses :twisted:

Use a Voltage / amp meter to check out vehicle plug, see what level of VDC your getting at socket, if 12 VDC is present then focus on your trailer.

If your meter has a continuity tester then pull your lamps apart and “ring out each wire from the plug socket to the pins on your lamps. Make a chart and cross them off as you go. I have also found sketching the wire circuit in troubleshooting wire problems is a big help You say “new wire harness” has it ever worked ? If it was just installed then make sure all you connection points are tight, I have see (once) on a new wire set, the insulation on the conductor wire was not stripped back far enough for the wire to make contact with the pins, therefore no current flow :oops:
 
I ment faulty ground as in my connector was grounding out

No, our rigs have seperate circuits for the truck and trailer. Trailer turn signal circuits will be fused at the dash junction, trailer park "running lights" are fused at the under the hood. Check the " trl park " 15a mini fuse, top left of the block. May not be your problem but the fuse is always your starting point
 
Loggerhead Mike, I owe you a beer. Thank you so much. It was actually just a fuse under the hood, the exact one you mentioned. I made the (incorrect and stupid) assumption that if the fuse were to blow, it would knock out power to the entire trailer. Alas, one replaced fuse and my hours of head scratching have come to an end.

Thank you to everyone that responded. I actually learned a lot and I greatly appreciate all the help. You guys are the best.

(and sorry again for the goose chase)
 
Loggerhead Mike said:
I ment faulty ground as in my connector was grounding out

No, our rigs have seperate circuits for the truck and trailer. Trailer turn signal circuits will be fused at the dash junction, trailer park "running lights" are fused at the under the hood. Check the " trl park " 15a mini fuse, top left of the block. May not be your problem but the fuse is always your starting point


Wow I learned something new (again…) that fuse must be very sensitive, without going much deeper into this it must use current load to sense resistance. That is a “SAFE” circuit.

Great job guys =D> :beer:
 
Glad that's all it was brother.

I went threw the same thing when I first baught my truck. The worst part is I was a mehanic at the chevy dealer at the time :LOL2:
.Loggerhead Mike, I owe you a beer.

Busch heavy please! :LOL2: :LOL2:
 

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