How to Wire a Cap/Topper Brake Light on a 2004 Ford Ranger XLT Extended Cab

[Garageguy60]

I looked back by the spare tire area, frame area, where the wiring harness starts to go through frame in back then heads towards the middle of the truck, and I DO NOT SEE and green wire taped off anywhere. I did find a trailer plug, a rubber plug with a little rubber cap connected to it. So I opened it up and saw one round prong and 3 round holes. So I went to NAPA store and bought a matching rubber plug with 3 round prongs and one round hole. Plugged both together,skinned off tips of 4 wires, a green wire,yellow wire,brown wire, white wire. Then at the cap brake light I have 2 wires coming from their, one Red wire and one Black wire. So I took those 2 wires and wired a disconnect to it (red to red, black to black) then I had my Wife get inside the Ranger and had her press the brake pedel as I touched the red wire coming from cap brake light and the touched the black wire to the white wire. the cap brake light comes on when the brake pedal is pressed, and goes out when taking foot off the brake pedal. So I thought that was correct. Just to mention, I tried touching the black wire coming from the cap brake light to the other wires (yellow,brown) with the pedal pressed and the cap light didnt come on, only when I touched to the white wire (black to white) so, when left turn signal is blinking, cap brake light DOESNT Blink which I believe thats how it should work correctly, When right turn signal is blinking, the cap light BLINKS,which it shouldnt work that way to be correct. So now im Puzzeld ????? What do I do to keep the cap light from blinking with the right turn signal on ????? PLEASE HELP ??? Thanks.

 

[PetroleumJunkie412]

Your truck is possessed.

The blinking cap light is the demon in your truck trying to communicate in Morse code.

Write down the blink sequence, but DO NOT translate it.

Contact your nearest priest that is certified in exorcisms, and relay the message.

Filling your windshield washer reservoir with Holy Water will help in the interim.

 

[ericbphoto]

Well. Here is what the 4 wires are that you found. Connecting your black to the white is correct. Your red wire could connect to either the yellow or green and it will work as a brake light AND as a turn signal for one side. Not quite what you want. We'll have to find a wiring diagram for your truck to figure out where to pick up just the brake signal. Usually that can be found back near the tail lights.

 

[ericbphoto]

I believe you were on the right trail looking for an unused plug with a light green wire in it. Connector C403 M. But I don't know where it is. You could pick up that signal at the cab mounted third brake light. But that's an awkward place to get it for your cap.

 

[pjtoledo]

I ran a wire from the hi-mount brake light on the cab back to the cap. if the cap has LEDs it won't draw much current.
or get a module.
3RD Brake Light Logic Module : 3RD Brake Light Logic Module (pacerperformance.com)

 

[sgtsandman]

It sounds like your taillights are like mine. With tail lights that have the turn signal and brake light in one bulb, you need an adaptor module to prevent the third brake light from blinking with the turn signal.

I need to change mine out. They burn out internally over time and cause the the third brake light to blink again. Mine is doing that after something like 10 years since it was installed.

 

[Patriot1]

Took my 100r to my local Leer dealer and 30 min later it was done. It works perfect and is super bright. FWIW.

 

[superj]

I connected mine to the trailer wiring harness under the bumper and it works fine. 04, also.

don't ask which wires though, that was long enough ago i cannot tell you from memory

 

[lil_Blue_Ford]

Took my 100r to my local Leer dealer and 30 min later it was done. It works perfect and is super bright. FWIW.

View attachment 85920

So, most cap dealers do the same thing from what I’ve seen. They pull the drivers side taillight, crimp a tap in the wiring for the taillights and put one of those logic boxes on that @sgtsandman mentioned and call it a day. It’s fast, cheap, and works…kinda.

IMHO, it’s not the best way to do it. The usual taps that they use to tap into the factory wiring allow moisture and corrosion into the factory wiring. If you live in an area like the rust belt, eventually this can become a problem because it not only can kill the brake light in the cap, but also the wiring to the factory taillight. My first truck and cap, that’s what they did. I had also opted for the additional light in the cap so they pulled that off the taillights too which meant that to use the light to see in the bed at night, the parking lights had to be on.

When I wired up the cap on my dad’s one Ranger and when I wired up my green Ranger, I ran wires back. Ground went to the battery. On dad’s I ran power for the bed light off the battery back too with a waterproof fuse by the battery. On mine since I have an aftermarket fuse block for accessories, I ran from that for the bed light. Now nothing has to be on to be able to light up the bed at night. For the brake light, on both I tapped into the third brake light wiring in the cab (solder and heat shrink because I don’t play games) and ran that back.

 

[Patriot1]

So, most cap dealers do the same thing from what I’ve seen. They pull the drivers side taillight, crimp a tap in the wiring for the taillights and put one of those logic boxes on that @sgtsandman mentioned and call it a day. It’s fast, cheap, and works…kinda.

IMHO, it’s not the best way to do it. The usual taps that they use to tap into the factory wiring allow moisture and corrosion into the factory wiring. If you live in an area like the rust belt, eventually this can become a problem because it not only can kill the brake light in the cap, but also the wiring to the factory taillight. My first truck and cap, that’s what they did. I had also opted for the additional light in the cap so they pulled that off the taillights too which meant that to use the light to see in the bed at night, the parking lights had to be on.

When I wired up the cap on my dad’s one Ranger and when I wired up my green Ranger, I ran wires back. Ground went to the battery. On dad’s I ran power for the bed light off the battery back too with a waterproof fuse by the battery. On mine since I have an aftermarket fuse block for accessories, I ran from that for the bed light. Now nothing has to be on to be able to light up the bed at night. For the brake light, on both I tapped into the third brake light wiring in the cab (solder and heat shrink because I don’t play games) and ran that back.

Good info. I have had several toppers wired this way and never experienced any issues. I suppose if I lived in the rust belt corrosion would be a problem. Then again there is always a better mousetrap.
So glad I don’t live in the land of sodium chloride winters - aka “rust belt”, I moved south and never looked back.

 

[ericbphoto]

The usual taps that they use to tap into the factory wiring allow moisture and corrosion into the factory wiring. If you live in an area like the rust belt, eventually this can become a problem because it not only can kill the brake light in the cap, but also the wiring to the factory taillight.

Don't even have to be in the rust belt for that. Those insulation displacement taps are horrible. I do have a few in the Ranger's toolbox for extreme emergency "get me home" repairs. But that's all. They are barely useful in temporary situations.

 

[lil_Blue_Ford]

Good info. I have had several toppers wired this way and never experienced any issues. I suppose if I lived in the rust belt corrosion would be a problem. Then again there is always a better mousetrap.
So glad I don’t live in the land of sodium chloride winters - aka “rust belt”, I moved south and never looked back.

Yeah, I live in the land of rust and ”green” wires. Even had a battery cable that looked perfect corrode to junk inside the insulation. Couldn’t figure out why I was having weird issues until I was pulling the dead battery again (like the 5th time in two weeks) so I could charge it and heard a crunch when I flexed the wire out of the way. Skinned off some insulation and found the problem. From that point on, everything gets solder, heat shrink (glue lined), and slobbered with dielectric grease.

That all said, there are ways to tap into wires without causing potential corrosion issues. They make taps that are dielectric filled. In a pinch you could probably make do with adding some grease to a tap that isn’t. It’s not really that much more expensive, but nobody seems to do it. The better method (what I use when I need to tap a wire), is pop the pin out of the weatherproof plug, remove a section of insulation on the wire, separate the strands, feed the end of my new wire between and twist it all together, lay my new wire next to the existing, solder, then feed heat shrink tubing (glue lined) on and shrink. Put the pin back in the plug and done.

 

[lil_Blue_Ford]

Don't even have to be in the rust belt for that. Those insulation displacement taps are horrible. I do have a few in the Ranger's toolbox for extreme emergency "get me home" repairs. But that's all. They are barely useful in temporary situations.

This is true, but they tend to last longer before a problem develops in areas that don’t suffer from major rust/corrosion issues. There was a time where I used them long before I learned what I do now. I have no idea where the last of mine currently are, nowhere near my electrical kit that’s for sure. I do keep the solder-shrink connectors on hand though (piece of heat-shrink tubing with a ring of low melt solder in them). I’d rather melt that on with a Bic than use a cheap tap.

 

[snoranger]

I deal with plow/ salt trucks… nothing will stop a wire from turning green. Heat shrink butt connectors with a second layer of heat shrink tube over it will slow it down, but that only gives us a few years. Copper anti-seize on the wire, a heat shrink butt connector, then a second piece of heat shrink tube over it seems to last the longest.

 

[Patriot1]

All good ideas gents. Thanks for posting! There is always a better mousetrap. My Ranger will likely never see snow or salt roads as we rarely see snow here. And being retired I usually wait a day or two until the roads are dry before hitting the road.