Sequencing Lights, Fords and Teslas: What Happens and How to Fix It
- john78372
- 3 days ago
- 4 min read
Someone called this week. He'd just bought a Ford Maverick, moved his bike rack light over from his old vehicle, and the turn signals had stopped sweeping. They flash now. Everything else works fine.
I knew what he was going to say before he finished, because I've had this call plenty of times. It's a known thing with Fords and Teslas, it isn't your light, and there's a straightforward fix.
Here's the whole picture.
What Actually Happens
It depends on the vehicle, and it's fairly predictable.
Full-size Fords. The lights typically don't work at all.
Compact and midsize Fords. Partial function. Usually everything works except the turn signal, which flashes the whole bar instead of sweeping across it. Running lights, brakes, all normal — you just lose the animation you paid for.
Teslas. Similar story, usually on the partial end.
Either way, the relay box further down this page sorts it out.
This Isn't a Kody Thing
Worth saying, because it's easy to assume a small manufacturer's product is the weak link.
Newer vehicles run trailer lighting through a lot more electronics than they used to, and the vehicle watches that circuit and reacts to what it finds. Search "trailer lighting module fault" and you'll find long threads on the F-150 forums, the Lightning and Tremor forums, and RV owners' forums — people towing boats, campers, utility trailers and U-Hauls, getting fault warnings while their lights work perfectly well.
There's a thread on F150Forum where owners wire an aftermarket tailgate light bar into the trailer connector, the truck decides a trailer is attached, and it switches off blind spot intervention.
On the Tesla side, etrailer put it plainly: the tow package can't detect LED trailer lights, because they don't draw enough current for it to register that they're there.
And the clearest sign of all — the relay box that fixes this is sold as a Tailgate Light Bar Signal Relay Box. It exists because tailgate light bars hit the same wall on the same trucks. A bike rack light is just one more thing you can plug into that connector.
Why Does It Happen? I Don't Know
I could write a confident-sounding paragraph here. I'd rather not.
My best guess is that these vehicles hold a diagnostic voltage on the circuit at all times and the sequencing driver can't reset against it — the basic flashing lights don't care, the sequencing one does. But that's a guess from someone who builds lights, not someone with a Ford wiring schematic on the bench.
What I can tell you is what I've seen across a lot of installs. That's enough to give you good advice, even without the mechanism.
Which Vehicles
Fords and Teslas.
With Fords it's broad enough that I wouldn't try to predict it from the model. I've seen it as far back as 2016 and I saw it on a Maverick this week. The severity tracks roughly with size — full-size trucks fare worst — but every recent Ford is worth planning around.
None of this is a knock on the vehicles. It's a design decision about how they monitor trailer circuits, it affects a lot of aftermarket lighting, and it is what it is. You just want to know about it before you order rather than after.
Two Ways to End Up Happy
This is the part that matters, and you get to choose.
If you don't care about sequencing, order a basic flashing light and none of this ever touches you. Our Medium never sequences — it's the simplest answer. The Large is fine too, as long as you choose one of the non-sequencing fixtures, since it does offer a sequencing option. The Small always sequences, so that one's out.
Worth knowing: going double isn't enough on its own. It's the light that matters, not the count. That catches people, and I'd rather you hear it from me.
The basic flashing doubles work properly on these vehicles. Occasionally one wants load resistors added to keep the vehicle happy about current draw, which is a known and solved thing.
If you do want sequencing — and plenty of people do, it looks great — you can absolutely have it. You just need a relay box in line. That's the next section.
That's the Small single 16-inch sequencing on a Thule rack, working the way it should. On a Ford or a Tesla, this is exactly what the relay box gets you back.
Still deciding on size? The buyer's guide covers that separately.
The Signal Relay Box
This is the fix, and it's why the man with the Maverick isn't stuck with a light he can't use.
The Signal Relay Box starts at $25. It sits in line between your vehicle's trailer plug and the light, separating your vehicle's signals from the light so the sequencing driver gets a clean feed. Nothing gets cut. Mount it, plug it in, run its power wire, done.
It also solves the problem retroactively — if you already own a sequencing light and just discovered this, you don't need a new light. You need a $25 part.
We sell it two ways, and the difference is worth understanding:
4-pin. The standard version. It needs a constant 12-volt supply, and most vehicles don't have one at the back, so you're running a wire forward to the battery or fuse box.
7-blade. Our own modification. It pulls power from the 12-volt trailer charge circuit that's already sitting in your 7-blade connector. No wire run, no trip to the fuse box. If you have a 7-blade, take this one.
Not sure which connector you have? Our guide to trailer connector types shows you how to tell in about thirty seconds.
If You're Not Sure
Send me a message with your vehicle, the year, and which light you have or want. I answer these myself and it takes a minute to tell you where you stand.
Better than finding out in a parking lot.
Find Your Rack
Kody lights for Kuat bike racks · 1Up · Thule · Swagman · QuikrStuff · RockyMounts · Yakima · Hollywood · Saris · Cravot · Rig'd Supply RamblerRack · Universal
Not sure which rack you have? Start at the lights by rack brand page.
Comments