Trailer Lights Gurus--Got a Question.

[npalen]

Amazon.com: iBrightstar IP68 Waterproof Square Trailer Lights kit, Red Brake Stop Tail Running License LED Light Lamp for 12V Camper Truck RV Boat Snowmobile Marine Under 80", DOT Compliant: Automotive

Buy iBrightstar IP68 Waterproof Square Trailer Lights kit, Red Brake Stop Tail Running License LED Light Lamp for 12V Camper Truck RV Boat Snowmobile Marine Under 80", DOT Compliant: Tail Light Assemblies - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

smile.amazon.com

Installed these lights on my little utility trailer and everything works correctly except the tow vehicle lights have to be on for any trailer lights to work.

That wasn't the case with the old trailer lights and everything works correctly on the pickup to which the trailer is attached.

I suspect this issue is related to the fact that the '03 Dodge Dakota doesn't have automatic lights, the switch has to be turned on manually.
I can live with this but wondering if there is a way "around it"?

TIA for any comments.

 

[sea2summit]

Sounds like a ground issue. Is it grounded well on the trailer side?

 

[CausticUrbanCoast]

Using a 7blade or 4pin connector?

 

[npalen]

The ground seems to be good.

It's a 4pin connector and everything works correctly as long as, at least, the "park" lights" are on.

I'm wondering if the light designer/manufacturer is "assuming" that no one still drives a pickup with manual lights,
(My wife tells me about all the things around our house that need "updating" Perhaps my pickup needs updating? Perhaps her husband needs updating?)

 

[Michael In Tennessee]

Do you mean brake lights don't work unless headlights are on? I'd check your truck on a different trailer and check the trailer on a different truck.

I do know newer Fords sometimes have problems with low impedance LED lights. The "smart" brake controller isn't smart.

Also, it could be ground. Run a ground wire externally to each light in turn to verify. On my trailer, I ended up with an intermittent problem. Eventually I figured out a ground problem. Its a tilt trailer and the trailer harness was grounded to the tongue and the lights to the frame. The frame/tongue pivot is old and corroded. The fix was a ground jumper at that location.

 

[CausticUrbanCoast]

The ground seems to be good.
It's a 4pin connector and everything works correctly as long as, at least, the "park" lights" are on.

With a 4 pin, no. It is not normally made that way unless you have a battery on your trailer for some reason.

With 7blade you could since it has a power supply line.

Edit: I usually switch any of my 4pin trailers to 7blade as I like backup lights on my trailers in the fall/winter or internal lights on the enclosed.

 

[nyone]

Are you sure the white wire is ground the way its wired up? Brown should be park/tail and yellow/green should be turn/brake. It sounds like your catching either a ground or power through the wrong side.

 

[npalen]

With a 4 pin, no. It is not normally made that way unless you have a battery on your trailer for some reason.

With 7blade you could since it has a power supply line.

I'm not following you here. What are you saying?

 

[npalen]

Do you mean brake lights don't work unless headlights are on? I'd check your truck on a different trailer and check the trailer on a different truck.

I do know newer Fords sometimes have problems with low impedance LED lights. The "smart" brake controller isn't smart.

Also, it could be ground. Run a ground wire externally to each light in turn to verify. On my trailer, I ended up with an intermittent problem. Eventually I figured out a ground problem. Its a tilt trailer and the trailer harness was grounded to the tongue and the lights to the frame. The frame/tongue pivot is old and corroded. The fix was a ground jumper at that location.

None of the light functions such as turn signal, brake lights, hazards work unless the pickup accessory (ignition) switch and light switch are on then all functions work correctly.

 

[CausticUrbanCoast]

I'm not following you here. What are you saying?

With a 4pin connector the taillights and signal lines are only energized when the vehicle's are.

Whatever the vehicle behavior is will be what your lights are: so if your vehicle has no markers unless the headlights are on, the same goes for the trailer

 

[npalen]

I think with all comments and things considered, the issue is no power to the trailer unless pickup lights are on.
The brown wire in the pickup's trailer connector will not show 12 volts unless the pickup lights are turned on.

I'm thinking now that the issue is the aftermarket trailer light plug-in adapter/harness that plugs into the pickup's light harness. It will only send power to the trailer if the pickup's lights are on.

I'm thinking now that the old trailer lights couldn't have worked either unless the pickup lights were on.

 

[npalen]

With a 4pin connector the taillights and signal lines are only energized when the vehicle's are.

Whatever the vehicle behavior is will be what your lights are: so if your vehicle has no markers unless the headlights are on, the same goes for the trailer

But the blinkers and hazards etc should work even if the pickup lights are off. (Ignition on) Right?

 

[npalen]

Edit: I knew this topic had the potential for an interesting discussion but I'm starting a headache.

 

[CausticUrbanCoast]

But the blinkers and hazards etc should work even if the pickup lights are off. (Ignition on) Right?

Blinkers should, hazards if they are wired that way, and none of the fuses are blown or trailer wires shorting.

The flat 4,5,6 and 7 should all have brakes combined with turn signals if you follow standard wiring.

The round 4 connector is not specified that way that I know of.

 

[herm0016]

it sounds like the ground is being switched by turning on the headlights somehow. get out your meter and test the polarity of the voltage from the ground in the plug to the one of the other pins with that pin on ( lights or whatever) i'm thinking it was wired backwards. an incandescent lamp does not care about polarity, and an LED does. so that could be the source of the difference be behavior. just a thought, as its an odd issue.

 

[npalen]

it sounds like the ground is being switched by turning on the headlights somehow. get out your meter and test the polarity of the voltage from the ground in the plug to the one of the other pins with that pin on ( lights or whatever) i'm thinking it was wired backwards. an incandescent lamp does not care about polarity, and an LED does. so that could be the source of the difference be behavior. just a thought, as its an odd issue.

Double checked the polarity and it is correct.

 

[CausticUrbanCoast]

DOT is dumb with lightning requirements, it is only recent that taillights were added to the daytime lighting requirements.

If your trailer light bulbs are of the dual voltage type, they expect your markerlight/headlight switch to be on. This provides a low voltage power to your trailer lights for the 4pin connectors. It was a cheap way for companies to provide the function without extra wiring.

You will only see 12V on the line if fully energized by the brakes or signal pulse. Otherwise if the marker/headlights are on you will see somewhere between 5-9V if I recall.

As a side note: this behavior will vary slightly depending on if your trailer wires were connected to the front or rear wires.

 

[npalen]

Bear in mind again that there is no power to the 4pin trailer connector UNLESS the pickup lights are ON. The trailer lights all work perfectly then.
Nothing can work if there is no power. The issue has to be in the pickup wiring, right?

 

[Doughknob]

Sounds to me like the truck's trailer wires are not connected properly. Does the same truck hooked up to a different trailer, work properly?

 

[flyerdan]

I would test the plug on the pickup with a DMM and see if it got the same signal that the vehicle lights did, that should isolate the issue.
You can also test the trailer with a 12v source (like an old power supply from a computer, who doesn't have a few of them around) and confirm that they work as they're supposed to.