Trailer wiring - running lights don't work

[Danimal]

Here's an interesting one...I have a Kia telluride sx and had the oem hitch and wiring harness installed from new. I finally got around to trying it with an enclosed 6x10 trailer and ran into an issue.

1) when I connect the 4 pin connectors and turn on the headlights, the trailer lights (approx 20 of them) flicker for one millisecond and then turn off. If I want them to flicker again, I need to turn off the headlights and turn them back on again and the same thing happens every time. When the flicker occurs, the running light plug loses power (checked this with A test light) until the headlights are turned off and on again. If I only use the test light, and don't connect the trailer, the test light stays lit up no problem indicating that power is running to that plug.

2) after getting frustrated, I decided to try another vehicle and sure enough all of the trailer lights worked immediately. I then tried another vehicle, and that one also worked lighting up all of the trailer lights.

3) eventually I tried the telluride and another trailer that only has 2 Running lights on it, and the running lights worked.

So what does that mean and where does it leave me? The enclosed trailer is working 100% fine with other vehicles, but not the telluride. The secondary trailer works with the telluride, but it has way less lights and not as much draw as the enclosed.

It sounds like there is a circuit breaker tripping to me, but I'm not sure if that's how these things are supposed to operate. The 30amp fuse has not blown in the engine bay.

I am going to bring it back to the dealer, but not sure how long it will take for an appointment.

Would appreciate some help, or advice if anyone else has run into this before

 

[2020Telly]

Occam’s razor suggests to me that the 4pin harness went bad or maybe has a loose connection. That’s where I would start having the dealer troubleshoot.

 

[G-23132]

Occam’s razor suggests to me that the 4pin harness went bad or maybe has a loose connection. That’s where I would start having the dealer troubleshoot.

With roughly 20 marker/running lights on the trailer, each one having 2 incandescent bulbs inside, for a total of 40 running lights I bet this is pulling too much power for the tellurides harness.

I used a volt meter and saw over 15V at the pin, so power is passing through the harness initially.

I’m super tired now from working on this all day, but tomorrow morning I’m going to pop out most of the marker lights and see what it does with most of the draw gone. I may still need a new harness, but this will be an interesting test!

I would really like to try another telluride and see what it does - that might narrow down whether these harnesses have a breaker in them.

 

[Danimal]

Occam’s razor suggests to me that the 4pin harness went bad or maybe has a loose connection. That’s where I would start having the dealer troubleshoot.

With roughly 20 marker/running lights on the trailer, each one having 2 incandescent bulbs inside, for a total of 40 running lights I bet this is pulling too much power for the tellurides harness.

I used a volt meter and saw over 15V at the pin, so power is passing through the harness initially.

I’m super tired now from working on this all day, but tomorrow morning I’m going to pop out most of the marker lights and see what it does with most of the draw gone. I may still need a new harness, but this will be an interesting test!

I would really like to try another telluride and see what it does - that might narrow down whether these harnesses have a breaker in them.

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[2020Telly]

Etrailer.com advertises two aftermarket harnesses for the Telluride one by Tekonsha and the other by Curt. Both advertise the same specs.

• Maximum amperage:
  • Stop/turn lights: 5 amps per circuit
  • Tail lights: 7.5 amps per circuit

You could ask eTrailer support if these would be enough to run the load you are drawing. I went through the little 8 page manual for the OEM harness and found a warning card:

• Maximum amperage:
  • Stop/turn lights: 4.2 amps per circuit
  • Tail lights: 5.5 amps per circuit​

 

[Danimal]

Etrailer.com advertises two aftermarket harnesses for the Telluride one by Tekonsha and the other by Curt. Both advertise the same specs.

• Maximum amperage:
  • Stop/turn lights: 5 amps per circuit
  • Tail lights: 7.5 amps per circuit

You could ask eTrailer support if these would be enough to run the load you are drawing. I went through the little 8 page manual for the OEM harness and could not find specs on the module. But I did take a picture of the troubleshooting page for you.

Thanks a lot, that's a great troubleshooting outline! Just getting up for the day and will be trying the market lights soon. If that doesn't work I'll be heading to the dealer next

 

[2020Telly]

You may just need to go aftermarket. Recheck my previous post. I was editing with the OEM specs while you replied. I think you are underpowered with the OEM harness.

This feels like another example of the 2020 Tow Option not being properly spec’ed to tow close to the max rating. They will get it right in 2021. +1 to waiting for better aftermarket over more expensive OEM.

 

[2020Telly]

One option to consider that will get you up and running is to add an in-line switch to the running lights. This way you can run with just tail lights and no running lights and then might lower the draw enough for your OEM to work. The other option is to just buy the harness from the trailer the install is very easy you just have to remove a dust cover.

Or you could replace as many of the bulbs with LED bulbs and that might also lower your draw on the trailer.

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[badpewterz]

another option that isnt a terrible idea is change the incandescent trailer light bulbs to led bubls (most are basic bulbs you can get bulk packs on amazon for cheap) this will lower the amperage alot and last longer

 

[2020Telly]

another option that isnt a terrible idea is change the incandescent trailer light bulbs to led bubls (most are basic bulbs you can get bulk packs on amazon for cheap) this will lower the amperage alot and last longer

I’ve seen some LED bulbs are only 20% of the amperage draw of their equivalent incandescent. And they last longer and good ones might even be brighter. Definitely worth considering.

 

[Danimal]

Thanks everyone for the replies! I hope this helps others on here as well, the tow package was definitely not well thought out - wish it had a 7 pin ready to go.

As mentioned in my last post, I pulled out most of the marker lights to reduce the draw and actually got the running lights to work. When I popped in one more light, it would cut out - so at that point it was enough troubleshooting to warrant purchasing 18 LED markers and upgrading them. I cleaned out all of the grime before swapping the new lights in and now everything works great and looks sharp.

I do have a flood light at the back of the trailer (on a toggle switch) that will kill the running lights when turned on, so my next step is to find an LED replacement for it to see if that will fix it.

 

[bh26]

Thanks everyone for the replies! I hope this helps others on here as well, the tow package was definitely not well thought out - wish it had a 7 pin ready to go.

As mentioned in my last post, I pulled out most of the marker lights to reduce the draw and actually got the running lights to work. When I popped in one more light, it would cut out - so at that point it was enough troubleshooting to warrant purchasing 18 LED markers and upgrading them. I cleaned out all of the grime before swapping the new lights in and now everything works great and looks sharp.

I do have a flood light at the back of the trailer (on a toggle switch) that will kill the running lights when turned on, so my next step is to find an LED replacement for it to see if that will fix it.

THIS!...this is why I love this forum. So many smart and experienced members lending input and ideas to one another!

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[Danimal]

Update again - I updated the two interior dome lights to LED, and the rear flood light with an LED unit. Now all 21 lights work together, but I do notice the interior lights dim a bit when I turn on the flood light at the rear so I’m probably right at the borderline for draw on the system.

When I have more time I’ll take it to the dealer and ask if trying another harness might help, but I’m no longer in a rush

That’s enough cursing for today...

 

[G-190367]

So here is "the same but different issue". I have a utility trailer that has an electric front jack which is nice when hooking up. The jack taps into the running lights on the Telluride. When I hit the switch for the jack the power goes out as well as the running lights. I have to then shut the lights off and on again to get the lights to work. So basically, my nice electric jack won't work on my new car.

 

[WayneTuttle]

Just had same thing on my 2 week old 2022. Worked at first, then changed to only short flicker at any light activation (tail, blinkers, etc ). Problem with actual trailer or with LED test plug. Problem resolved by removing and reinserting connector. Not sure if it was resetting power to unit or just disturbing the connector. Access is behind plastic cover behind left rear tire under car