Third Brake Light?

[Optimistic_Para]

The third - upper - brake light on my Ford pickup is completely blocked by a truck camper. I don't think I've ever seen a truck camper that has one. Come to think of it, I can't remember ever seeing a trailer that has one, either.

What's up with that?

That third brake light is such an obviously good idea that I can't believe they don't come as standard.

I do see them with 5 lights across the top - two at the outer corners and three clustered together in the center - and I think I remember reading something about DOT required lights on certain widths of truck bodies and trailers. Apparently DOT doesn't require the upper brake light.

Has anyone here added an aftermarket third brake light to their camper? How hard would it be to do? If I do it, am I going to see flashing red lights in my mirrors?

[MORSNOW]

Zig wrote:
It does seem odd that truck caps are required to have the third brake light, but slide-in truck campers do not...

Truck caps are probably classified as a truck accessory, while truck campers are an RV/Cargo. Cargo can block rear windows and don't require 3rd brake lights.

[Zig]

It does seem odd that truck caps are required to have the third brake light, but slide-in truck campers do not...

[Grit_dog]

Optimistic Paranoid wrote:

AnEv942 wrote:
If you tap one of the taillights the CHMSL will flash with that light. Tapping both will give you constant signal from light that isn't flashing. Requires diodes (or little magic box) on the taillight leads so not back-feeding each other.

Thank you. That makes sense now.

Would probably be easier to add 2 additional turn signal/brake lights, 1 on each side. Then it's a direct splice to each light from the lower ones.

[JRscooby]

Much easier, IMHO would be add extra lamp on each side. More brake light and more turn light. More tail would not hurt ether if not to high.

[northshore]

A couple of things here;
first, why I don't know for sure I would venture to guess financial. It cost money to include a 3rd brake light. Just a guess on my part.
second, if being visible is in the equation, then the led conversion taillights makes sense to me. There are quite a few You tube vids on making the change over. Im thinking about this route. myself.

[stevenal]

AnEv942 wrote:
Tapping both will give you constant signal from light that isn't flashing. Requires diodes (or little magic box) on the taillight leads so not back-feeding each other.

With diode isolation, the on will override. Signal to turn and the 3rd light will flash until the brake is depressed and it becomes solid. Legal?

[Dave5143]

With all the distracted driving on our highways, a third brake light isn't going to do much. I was going to mount a CHMSL on my trailer till I realized it wasn't worth the effort. People still can run into you.

[BB_TX]

Optimistic Paranoid wrote:

AnEv942 wrote:
If you tap one of the taillights the CHMSL will flash with that light. Tapping both will give you constant signal from light that isn't flashing. Requires diodes (or little magic box) on the taillight leads so not back-feeding each other.

Thank you. That makes sense now.

Even with diodes the center light would flash if you initiate a turn signal without applying the brakes, or until you do apply the brakes. That’s why you need an electronic circuit to detect both lights on/both lights off to prevent the center light flash.

[Optimistic_Para]

AnEv942 wrote:
If you tap one of the taillights the CHMSL will flash with that light. Tapping both will give you constant signal from light that isn't flashing. Requires diodes (or little magic box) on the taillight leads so not back-feeding each other.

Thank you. That makes sense now.

[wnjj]

stevenal wrote:
And to the same filaments when signalling to turn or switching on the flashers. Most of the time stopping and turning occur simultaneously, so one filament is solid while the other flashes. Which side should they wire the third to?

It would have to be done with a digital circuit that lights the 3rd light after sensing both lights were on simultaneously. Then it would stay lit as long as at least one is lit constantly so it wouldn’t flash with the hazards (other than one initial flash).

[AnEv942]

Tapping Domestic truck lights -both.

I've thought about adding 3rd brake light (CHMSL) before.
Issue is adding something not just stuck on and hiding the wires.
Our camper door is centered so ideally light would be on door (or behind window) which makes wiring considerably more involved.

Second is brake signal.
Part of the requirement for 3rd brake light on trucks also added that a wire be run to rear for addition of 3rd brake light. IE camper shell/topper etc. Somewhere at rear is a 3rd brake light wire stubbed.

That said, for a slide in camper still not practical getting that wire to camper (if you have dedicated 7pin bed plug you 'could' use trailer brake pin). You'd need to run a wire from where your umbilical terminates inside to rear of camper to light. Painful on ours

So I would tap the campers brake/signal wires (if I could get past sticking light on door). Which one? Both. (Unless your taillights have separate bulbs for brake and signal.)

If you tap one of the taillights the CHMSL will flash with that light.
Tapping both will give you constant signal from light that isn't flashing. Requires diodes (or little magic box) on the taillight leads so not back-feeding each other.
Edit:
While easy to do for brake light- center light flashing is not legal in many (if not all) states.

[stevenal]

And to the same filaments when signalling to turn or switching on the flashers. Most of the time stopping and turning occur simultaneously, so one filament is solid while the other flashes. Which side should they wire the third to?

[Reality_Check]

There is rude, and then there is pointing out the obvious. Not the same.

Why isn't there one? Typical domestic vehicles need only a three wire, plus ground, system for lights. One for right, one for left and tail. The left and right also act as the brake for those lights. The third light obviously isn't tied into those, or it would blink every time you used a signal. It's on it's own lead.

So to run one on a trailer/TC through a plug, it would require a separate feed. I personally wouldn't trade the one aux left (from a 7 pin) for a third brake; I want it for my back up lights on the trailers.

7 pin: Hot, Ground, Brake, Left, Right, Tail....and Auxiliary. It's a choice with the systems we have. Or we can redesign the wheel and go with 8 pin....

[Optimistic_Para]

For the record, I'm not worried about being rear ended because I don't have a third brake light. I drove vehicles that didn't have such a light for many years. Nor am I worried that I'll be arrested for putting an aftermarket one on my camper.

I'm simply curious as to why they don't come with them, and I was wondering if it might be because of some stupid, outdated bureaucratic regulations.

I'd forgotten just how broadly diverse the RV community was here. We clearly have all kinds of people here - including a few rude idiots.

As for the lack of a dedicated wire, or the need for a converter, I'm clearly missing something. We already send power to both the left and right tail lights when we step on the brakes. Why could the same power not also be routed to the third light?

Perhaps one of the more knowledgeable people here could - politely - explain it to me? Thanks.