Blinking lights on the trailer when parked?

[Pacific.NW]

I was doing “truck things” with my truck yesterday and rented a trailer to haul small landscaping equipment. Everything connected properly and the light check was good. I went out for a walk in the evening (the trailer had been left connected) and noticed the tail lights of the trailer would blink a very dim but noticeable pulse every 2s or so.

I typically pull a small travel trailer using the old school 4-pin connector and have never noticed this before. I figured either this was a safety thing to make the trailer more visible (even if the blink was dim), or there is some weird fault in the electrical causing a blip on the lines.

It was at this time I discovered another fin fact about the Lightning and a trailer… if you unplug the trailer electrical while your vehicle is locked, you will set off the alarm (if it’s enabled)!

So I’m standing there trying to fumble with my app to get the vehicle to stop honking and because I’m still connected to my home’s wifi, but not close enough to get a decent signal, the app is showing blank boxes where the buttons should be. It was a bit of a comedy of errors but managed to get it to stop.

Anyone else notice the blinking or alarm quirk?

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[RickLightning]

The alarm is not a "quirk", it's an anti-theft feature. If you don't want it to go off, simply unlock the truck.

 

[Pacific.NW]

The alarm is not a "quirk", it's an anti-theft feature. If you don't want it to go off, simply unlock the truck.

Yeah, I figured that out after the fact!

 

[chriserx]

It actually explains the blinking, it likely is checking to see if the trailer is attached. Wonder if you could swap out for one of those portable hitch lights and get away with it Indiana Jones style...Or would the parking pawl release and have the truck chase you down the street....

 

[Pacific.NW]

It could be checking for the connection, but I’d think it’s possible to do that through continuity on the ground…?

 

[RLXXI]

It could be checking for the connection, but I’d think it’s possible to do that through continuity on the ground…?

Most likely it's looking for a voltage drop. Vehicle is insulated from ground via the tires.

 

[Pacific.NW]

I meant ground as reference to the 0v line.

 

[RLXXI]

I meant ground as reference to the 0v line.

Negative circuit, gotcha. I don't know if they still use the same strategy as my 2013 xlt but it's system has a negative pulse circuit where bat+ is constant. I need to dig deeper into these new systems, hard to keep up with it all after you leave the dealer.

 

[chriserx]

out of curiosity, is your trailer lighting LED or traditional bulbs, I'd think that traditional bulbs wouldn't have time to illuminate before power was cut unless it were pitch dark outside

 

[hturnerfamily]

I've noticed this on all my Campers with LED tail lights or running lights, etc... there is simply a small amount of constant/variable 12v power that is causing this phenomenon... and you'll likely not see this if the coupler is not on the truck's ball, but still 'plugged in' to the truck's 12v outlet.

While I've never had the 'alarm' go off just because I detached or unplugged the camper, likely I've also never had the truck locked, when doing so... thankfully.

 

[Adventureboy]

It could be checking for the connection, but I’d think it’s possible to do that through continuity on the ground…?

It is very likely a continuity check heartbeat. The LED lights on trailers today are quite efficient and that "pulse" might only show up on some trailers with very efficient lights, and probably only when the truck is locked and armed. Disconnecting it while it is armed means it doesn't receive the heartbeat and sets off the alarm.

 

[Pacific.NW]

out of curiosity, is your trailer lighting LED or traditional bulbs, I'd think that traditional bulbs wouldn't have time to illuminate before power was cut unless it were pitch dark outside

They’re LED - and it’s very dim, so just enough voltage to cause it to blink.

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