Hi Guys/Gals

I can't find the information I need on the net so I respectfully request some professional help.

Subject: Homemade wiring harness for towing. Trailer, boat, whatever.
Type: 4 Flat
Vehicle: 2003 Dodge Caravan.
Problem: No brake lights on trailer.

What I have working right now: Left & Right turn signals and running lights.
Can't figure out what to do to get the brake lights to work.
I have all necessary tools to complete whatever you guys/gals recommend.

How can I make the brake lights work?

Thank you all sincerely,
John

 

Do you have amber turn signals in back? If you do, you can't wire the lights direct. You'll need a wiring harness adaptor that has a logic circuit to separate the turn signals from the brake lights. Without it, you'll either get turn signals, or brake lights. Not both. They run around $30-35. They wire up easy and work great, first time every time.

 

Have you confirmed that the brake light signal is working at the 4 flat connector?

 

No... it's just a small 4x8 flatbed. Just two small round tail lights on the very back.

Like these: Actually looks exactly like these


Thank you,
John

 

Well GumbyRT... it's a 4 flat so I have confirmed that the left and right blinkers are working on the trailer. So... the brake lights are supposed to work on the grn and yel wires just like the turn signals.

Thank you,
John

 

This is the wiring harness I used which is vehicle specific (I have a 2018). If you look at the wires on the bottom right in the initial pic on the page you can see a brown and a yellow wire coming out, where as on the left rear wires you only have green coming out. If I'm not mistaken one of the rear wires becomes the brake light wire since the bulb that is for blink is the same light bulb you use for brake lights. Also did you verify you have brake lights on both sides of the vehicle? Because if a bulb is burned out that could also be the problem.

 

I’m aware of how it’s supposed to work, but that doesn’t mean it’s working like it’s supposed to be.

It’s easy to assume that having turn signals means you also have brake lights but there’s a reason assuming anything is a bad idea. I’ve worked on far too many trailer lights to know better.

Apparently you meant something else when you asked for professional help...

 

You will never get your lights working properly until you use a wiring adapter with a logic circuit. If you have the red tail lights, what you're doing would work fine. When you have a vehicle with separate amber turn signals, you MUST have the logic circuit to separate the brake lights from the turn signals. I went to the Autozone site and put your car in and this is what they sell

https://www.autozone.com/trailer-wir...66682_977776_0

It's cheaper than I thought. My daily driver is a Mazda CX-5 and it requires the logic circuit for proper tail and brake lights. In the late 80's and into the 90's, imports needed the adapter and after 2000 or so, a lot of domestic vehicles got the same treatment.