How to: 3rd brake light install

[kach22i]

Originally Posted by testa-rossa

Now, where do I look for the brake light?

Originally Posted by kach22i

This is as clear as I can make it.

[bugstrider]

Kash221,



Do you know what the loose connection is that is exposed? It's the one directly under your drawn circle and straight up from your volt tester prong. It has Hella embossed on it. I have the same one but can't find what it is suppose to go too.

Non existing rear fog maybe ???

I'm in the process of tapping wires for my third brake light.



Cheers

[kach22i]

Originally Posted by bugstrider

Do you know what the loose connection is that is exposed?

I don't know what it is, fog lights is a better guess than trailer lights though.

If it ain't broke, I don't fix it.

My weight loss program is getting delayed another day (working on a house Monday now), just a little more to do on my buddies house before we can leave for a while. Swinging a hammer is a nice gig short term, but I don't see how a body can hold up to it over a lifetime.

I hope then to get some of the removed parts off to people which can use them.

[bugstrider]

Hahaha,

I know that idea well....
Our connection is so crusty it's never been used, so I am not too worried. Speaking of broken, while running lights per your post, I discovered a long bolt under my air pump. Being the curios type, I look around then the phrase "Holly S#€£, you have got to be F%¥€-ing kidding me" slips from mouth. The anchor bolt that holds the air pump to the engine was out and lying under the unit. The only thing holding it on was the tension bolt and drive belt. The rubber shock/vibration plug was even torn in two. I can only imaging the chaos that would have ensued had it totally separated at 3-4k rpms.

So, where I am going with all of this is.... Because of your pearls of wisdom on where to run our third brake light wires, I found this little time bomb. THANKS AGAIN!!! You saved me some major pain!!!! The silver lining is that I was able to check other connections and bolts. Located a missing bolt on my shroud, quick fix. I am hoping this is an isolated event. Got the third light hooked up, very bright which is a bonus. Although, my E-brake lamp is now constantly on. Now I just need to track down that gremlin and squash it.







So the moral to this story, make sure your *** has lock nuts or washers.

Cheers Trev


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[bugstrider]

Original source to the E-brake solution.

1978 911SC - Rear Brake lights Out and E-Light ON

Another little nugget to keep in mind. In all of our brake light adventures, you may discover your "emergency brake" light mysteriously always on after the repairs. In reading older posts, the always on light could be an indicator of a couple of pending problems, such as a bulb, MC switch, Voltage regulator or alternator charging problem. In any case, to reset the system, while the ignition is in the "on" position,(engine NOT running), disconnect the negative side of the battery. Leave it off for approx a minute, reconnect. This should clear the system fault. When I started the car, the light was out and functioning properly.

Again, this information s being passed on from older posts. I hope this helps any who are experiencing the same type issues.

Our end result of our new eye grabbing third brake light....

[testa-rossa]

I'm home sick today so I thought I'd give it a try. I successfully wired the brake light using the included clips with the kit.

One problem. The light is dim even when the brake isn't being touched. Once I press the brake then it lights up nicely.
Brake pedal NOT being pressed


Brake pedal being pressed:


any thoughts as to why the brake light is partly illuminated when i'm not touching the brake pedal?

Thanks,

tyler

[bugstrider]

What line did you tap into for power? If you are using the light from DS, it's either on with the brake lights or off. You might have some other underlining back current going on.


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[testa-rossa]

I tapped into the black cable with the yellow stripe.

[bugstrider]

Ok,

That's the same one I used. What about your ground and the type of connector used for the tap? What about the condition of your bulb connectors? Because I had connection issues, I ended up really giving my housings a good once-over. Tightened connections, cleaned terminals, even gad to make a repair to one housing because I was a bonehead. In the end, my regular tail lights are stronger than before.

It's as if you could be getting some residual current., and your% sure the light has a slight glow? Did you check the light itself? The Hella led housing pops off so you can adjust the angle of the led lens.

Who did you get the light from?

Trevor

[testa-rossa]

I got the light from Daniel Stern. I'm 100% sure the lights are dim when no brake pedal is pressed. I am using LED bulbs in the tail lights. I'll try using the regular filament bulbs to see if that makes a difference.

my tail brake housings have seen better days... as I'm sure all of ours are the same. it could very well be something in the rear brake lights themselves.

[bugstrider]

If you haven't done so so already, shoot Daniel Stern an email on your symptoms. Be very specific and detailed on the steps taken, connections, how, where, etc. he would be better suited to guide you on all matters related to this light. I guess there is the very slim chance the light itself could have an issue but I doubt it to be honest.

He will be able to give you more accurate solutions.

Trevor


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[kach22i]

There is a trouble shooting thread or two on LED tail lights if you do a search.

[carl74344]

I still like the old school look. I will change the bulb for LEDs soon.

[fintstone]

Do you have rear fog light on?

[testa-rossa]

I don't believe my car has rear fog lights???

[kach22i]

FYI: link to large wiring diagram labeled "Wiring Diagram Type 911 S".
http://www.pelicanparts.com/911/911_parts/Electrical/911_electrical_1965_911S.jpg

Many more wiring diagrams here:
http://www.pelicanparts.com/911/911_parts/911_electrical_diagrams.htm

I guessing my unhooked mystery connector is for a missing rear engine lid compartment light.

[fintstone]

Testa-rossa. The light had two wires. You hooked one to the black/yellow. Where did you attach the other one? Must have not hooked it to chassis or a brown one.

Also, what year is your car?

[testa-rossa]

Fintsone, i connected the red/black cable to the black cable with yellow stripe. Then I connected the black cable to a bolt that connects directly to the car body. I tried a number of different areas and this one seemed to work the best. My car is a 1985 version.

I sent an email to Daniel Stern. Here's his response:

Wow...that's interesting! I have not had any previous report of this issue before. Assuming the central stop light is hooked up correctly (+ wire to brake light feed, - wire to ground) then it cannot be a fault in the central stop light, which simply responds to whatever power is put across it. It would have to be an issue with the vehicle's own wiring, something causing current leakage to the brake lights. You may want to apply a voltmeter or test light to the car's left and right brake light sockets to see if you see voltage there. I'm not 100% confident in my recall, but I think your 911 uses a hydraulic stop light switch -- those can go faulty in this manner. It wouldn't necessarily show up visually as dim light in the incandescent left and right stop light bulbs. It's to be hoped the issue is simple like that -- more arcane wiring faults can be a real bear to hunt down!

[fintstone]

I agree with Dan. It seems almost impossible for this not to work....the circuit is so simple. Is the light on all the time, when the engine is running, or when the key is switched to on?

Perhaps your LEDs are causing the problem as you suggested...but I really don't know how. Did you try just removing them to see what happens/if that light goes out??

[testa-rossa]

Ok, was able to put a volt meter to various parts to try and diagnose why the third brake light stays lit when no brake pressure is applied.

We unplugged the rear tail lights and put a volt meter on each of the pins. We verified that the we get 12 watts on the black and yellow wire when the brake pedal is applied. Then we lifted the brake pedal and I noticed that I got 4 watts still coming through the wire.
Then we unplugged the cable from the master cylinder. 12 watts coming from the wire to the fuse but we were getting 4 watts from the black and yellow wire there too?



Very confusing. Now, i'm not sure what to do or how to diagnose this thing. Is it possible that the black and yellow wire is getting volts from somewhere else? Maybe a short somewhere?