No running lights

[DwnHomeCntryBoy]

I'm not sure when it happened... but the running lights on the trailer is blowing a fuse on the truck.

I know they were working when we left a previous location; we do light checks every time we hook up before pulling out. When we got to our next location, the wife says she remembers seeing them on when we pulled in as she had to get out to help guide me into the pitch black spot. When we left that location, no running lights during light check.

*verified it is the trailer as with it unhooked, truck no longer blows fuses and when jumpering the trailer plug, it is blowing the fuse in the jumper

I've pulled all the bulbs out (switched to LED bulbs years ago) and inspected all exposed wiring for any nicks (none found). Short of pulling the underbelly off and inspecting every inch of wiring, any ideas on something specific to check?

And it is only the running lights. Good brake, tail and turn lights.

 

[xxmxracerxx]

I personally would start with a fused jumper wire. Assuming the fuse is a 10A that is blowing I would use the same and jump the trailer connectors ground to running lights in the 7-way. If it blows the fuse, then you know for sure its trailer side. And if it is I'd start with checking the connections within the 7-way if it is serviceable making sure the wiring is not grounding itself or shorting to voltage within those pins. If it is not a problem with the trailers 7-way checking the wiring from light to light is not all that bad. You can use voltmeter and remove the lighting and check for continuity on that circuit from light to light. If the problem is on that circuit, then you will have an open on that circuit and can run a new wire. Same goes for ground wiring.

If it does not blow the fuse check your truck side 7-way for corrosion buildup. Also, the connector behind the bumper to your 7-way could also have some corrosion.

Hope this helps.

 

[cookie]

There are a couple things you can do to track down that short, some already mentioned.
You didn't mention if a fifth wheel or bumper pull. If a fifth wheel there is a junction box located behind the pin box. You can open that, disconnect the running light wire and check the umbilical cord for short to ground. Take a picture of all the connections before disconnecting anything. If a bumper pull there should be a box on the frame, you can open that and check the same way.
You could also remove all the running lights, plug into your truck and see if you still blow a fuse. If yes you know there's a problem in the wiring. If no blow start replacing the lights one at a time till you blow a fuse. That would be the culprit.
I say that about the bulbs because I just had a similar thing happen in our sticks and bricks. It was an easy track down though as I could smell it. One month old LED failed.
Good luck and be sure to come back and let us know what you find.

Peace
Dave

 

[DwnHomeCntryBoy]

I personally would start with a fused jumper wire. Assuming the fuse is a 10A that is blowing I would use the same and jump the trailer connectors ground to running lights in the 7-way. If it blows the fuse, then you know for sure its trailer side.

It's a 20A on the truck and it is trailer side

*verified it is the trailer as with it unhooked, truck no longer blows fuses and when jumpering the trailer plug, it is blowing the fuse in the jumper

And if it is I'd start with checking the connections within the 7-way if it is serviceable making sure the wiring is not grounding itself or shorting to voltage within those pins. If it is not a problem with the trailers 7-way checking the wiring from light to light is not all that bad. You can use voltmeter and remove the lighting and check for continuity on that circuit from light to light. If the problem is on that circuit, then you will have an open on that circuit and can run a new wire. Same goes for ground wiring.

Plug is not serviceable... no way to check wiring in it.

I only tried to meter one light and it did not meter how I thought it would (one side +12V, the other GND). Somewhere along the way, the orange cover came off (two did... both front corners oddly) and the price of just the cover was the same as getting a new LED housing. I metered the wires to find out which was positive (although I'm not convinced it really matters) and both wires metered +12V when connected to the positive terminal on the battery. Both wires also metered good continuity to both the ground and positive battery terminals as well as between the two light prongs. I metered the other 5 running lights (the lower ones) and they also had good continuity between the two light prongs

 

[DwnHomeCntryBoy]

You didn't mention if a fifth wheel or bumper pull. If a fifth wheel there is a junction box located behind the pin box. You can open that, disconnect the running light wire and check the umbilical cord for short to ground. Take a picture of all the connections before disconnecting anything. If a bumper pull there should be a box on the frame, you can open that and check the same way.

Bumper pull... 2017 Mallard IDM312. There is a box there on the frame and that was going to be the first place I planned on digging into when I have time for a more in-depth look.

You could also remove all the running lights, plug into your truck and see if you still blow a fuse. If yes you know there's a problem in the wiring. If no blow start replacing the lights one at a time till you blow a fuse. That would be the culprit.
I say that about the bulbs because I just had a similar thing happen in our sticks and bricks. It was an easy track down though as I could smell it. One month old LED failed.

I went through 4 of the box fuses (first was how I knew there was a problem, second was verifying fuse was blowing, third was after cleaning truck and trailer 7-pin connections and fourth was after rewiring connections on truck side.
Once home, first mini-fuse was fused jumper to verify, second was after pulling the six lower LEDs and the third was after pulling the upper five on the back.

 

[xxmxracerxx]

Ok, since you confirmed it to be trailer side blowing 20A fuse. There is a way to check wiring in the 7-way. As cookie stated - open your junction box and find the green wire and remove. Using voltmeter check continuity at pin 3 (top right from top notch) to removed green wire on box.

Are the marker lights and clearance lights inop or just clearance and/or just marker?

Might need to get under coach and look at the wiring for chafing or detached wiring at lighting points.

 

[DwnHomeCntryBoy]

Ok, since you confirmed it to be trailer side blowing 20A fuse. There is a way to check wiring in the 7-way. As cookie stated - open your junction box and find the green wire and remove. Using voltmeter check continuity at pin 3 (top right from top notch) to removed green wire on box.

Are the marker lights and clearance lights inop or just clearance and/or just marker?

Might need to get under coach and look at the wiring for chafing or detached wiring at lighting points.

It's all of the lights that are connected to the running lights wire (top right connection). Left, Right and Brakes are all functioning correctly.

I looked at all of the exposed wiring for each light and no signs of wear between light and where it runs under the trailer and four of the lower lights (orange in middle and red in the rear). The two orange lights in front and the five up high in the rear have the wiring all contained inside the trailer. (I have not done anything to the two orange lights up high in front to try and inspect or remove them as they are also contained within and are still factory lights)

 

[xxmxracerxx]

I'd still check 7-way to green wire in box to #3 pin if haven't already. It also kind of seems to be a critter chewed though some wiring. You can pull the lens off each light and remove the base to access the wiring. A power probe would be handy in this case.

 

[DwnHomeCntryBoy]

I'd still check 7-way to green wire in box to #3 pin if haven't already. It also kind of seems to be a critter chewed though some wiring. You can pull the lens off each light and remove the base to access the wiring. A power probe would be handy in this case. View attachment 67888

Yea, I'll check the junction box before I dig too much further into anything.

Is there another diagram? It looks like just a generic "every trailer is wired like this", but I haven't found one while searching and looking for something that's a little cleaner to read.

 

[DwnHomeCntryBoy]

Found the image you copied in another uploaded manual.

This does at least confirm of what I thought that it didn't matter which wire from the light was hooked up to as they're just tied together in series.

 

[xxmxracerxx]

Yes, found that in this forum. I believe I've read in here for the specific model could try contacting Heartland and have them send you the wiring diagram as ones provided with the RV is mostly a generic and does not specifically match what we own. If I am wrong, I'm sure someone will correct me. This forum has helped me a lot since joining.