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YOUR RESEARCHLoad resistor for LED 3rd Brake Light
Reported or suspected cause
adding the led 3rd brake light too
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Leading evidence: 'adding the led 3rd brake light too' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'adding the led 3rd brake light too' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Check actual wiring in the '99 wiring diagram' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Reported cause
Cruise was working again....so we know for sure it was the LED tail lights.
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I checked the fuse which is a 15w located at B-7 which is labeled 'brake light/cruise control' and it is just fine...brake light works fine too.
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The resistors were already installed on them so no problems.
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Suggestion
If both 3rd brake lights were replaced by LED, all you need is to wire a 6~8 ohm 50w resistor in parallel to ANY of the brake lights including the rear brake lights.
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Suggestion
So I was thinking of running the parallel resistor across the ground and power for the brake lights somewhere between the body and the 6 pin connector.
resistance...on the spyder lights you are alluding
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I think the issue is the resistance...on the Spyder lights you are alluding to, you use the conventional incandescent brake lights from the original lights...the DEPO is 100% LED which make the resistance fall too low...
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I have now upgraded all of my tail / brake lights to LED. When I connected the 3rd brake light, I got the ABS/PSM warning lights. I was thinking a led load resistor from Autozone would be the easy fix. Any suggestions on what i need? How to install?
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I want to do this mod, too. What LED upgrades did you use? I also want install a strobe module to make the 3rd brake light flash when applied (I have this on my Harley)
All brake lights + the 3rd brake light is about 60W in total. I think these will work.
Connect one in parallel to any of your brake bulbs and see if that works. If not, connect both of them in parallel.
Amazon.com: CUTEQUEEN TRADING 2PCS 50W 6Ohm LED Load Resistors for LED Turn Signal Lights or LED License Plate Lights or DRL (Fix Hyper Flash, Warning Cancellor) or stop brake with 4pc Quick wire Clip: Automotive
Amazon.com: CUTEQUEEN TRADING 2PCS 50W 6Ohm LED Load Resistors for LED Turn Signal Lights or LED License Plate Lights or DRL (Fix Hyper Flash, Warning Cancellor) or stop brake with 4pc Quick wire Clip: Automotive
It does not matter electrically as all the brake light bulbs are wired in parallel but I would think for easy access it's good to connect the resistors to one of the tail light housings.
Yes, brown means ground for most German cars.
Need some additional help. I have installed both resistors.
http://www.amazon.com/CUTEQUEEN-TRADING-Resistors-License-Cancellor/dp/B00GQ2TC14/ref=sr_1_3?ie=UTF8&qid=1431103834&sr=8-3&keywords=6ohm%2050w%20resistor&tag=viglink20410-20
http://www.amazon.com/CUTEQUEEN-TRADING-Resistors-License-Cancellor/dp/B00GQ2TC14/ref=sr_1_3?ie=UTF8&qid=1431103834&sr=8-3&keywords=6ohm%2050w%20resistor&tag=viglink20410-20
One per tail light. Still getting PSM and ABS lights. I'm assuming it doesn't matter which way is which (+ / -) since they are both the wires are red?
That's even better as it wastes less energy with higher resistance. What you did on the tail lamps should have worked though. Oh well, it's working now and that's all that matters
I had installed the Depo tail lights and now the smoked third brake lights and lost my cruise functionality.
It seems to be common since what I am reading is that in addition to the 50w 6ohm resistors for the tail-lights, you would also need the resistor for the 3rd brake light.
The issue is do I need one for the recessed one as well as the one in the electric spoiler? If so, how did you mount your resistor for the lights in the spoiler when you should not attach it to plastic because of the heat generated?
Any input would be appreciated.
Running the resistors in parallel gives the circuit multiple paths to completion, decreasing total resistance.
Example: If you install two 12-ohm resistors in parallel, the total resistance is 6 ohms. If you install two 12-ohm resistors in series, the resistance is 24 ohms.
Installing resistors without understanding this concept isn't a great idea...
I agree.
I know to run them parallel to the circuit and that is not a problem.
The issue is first, whether I would need a resistor for each of the two third brake lights (one in the recessed cowl and the other in the electric spoiler)? I believe I will need one for each in that the recessed one does not work by design when the electric spoiler is up and the one in the spoiler 'takes over.' So it seems that they are separate depending on whether the spoiler is up or down.
The second is if the first is in the affirmative, then where would you mount/secure the resistor since the third brake light in the automatic spoiler is essentially plastic (not wanting to mount something that would heat up on plastic)?
Any ideas/photos are appreciated.
Thanks.
I couldn't find a diagram to answer your first question. Since the resistor will only heat when you're on the brake, do you anticipate it getting enough use to melt the light assembly? Options would be to secure it using an adhesive that doesn't conduct heat well and/or using a heat sink on the resistor in that location...
My thinking was like yours, mounting it to the back of the unit itself would be the easiest. However, wherever you look, the general warning was to avoid such.
The 3rd brake light on the 996 MK1 (mine is a '99) actually only has a hot and a ground.
I agree, a good 3M adhesive double sided tape would be my thought too on the back of the LED housing since you would not anticipate long periods of braking with the spoiler up.
So do you agree the spoiler brake light would require a separate resistor too?
I believe the first applies to the 3rd brake light on the 996 MK-1.
Ordered my LED's from Del Rey Customs for about $700 for tails and 3rd brake. Plug and play, built in resistors. No warning lights. Work as advertised. Love the updated look.
Do your depo LED lights already have built-in resistors? If they do, you may need an extra 6~8 ohm 50W resistor (to create a similar load of the 3rd brake light) wired in PARALLEL to ANY brake lights as the the brake lights are all wired in parallel sharing the same power source that comes from the brake light switch.
You could always test the resistance across one of the circuits before and after adding a resistor to the other circuit. If you see a corresponding change, you'd know that one resistor is affecting both light circuits...
A diagram would be better than poking around with a multimeter, but if all you have is the multimeter...
*edit* or Ahsai might pipe up at any moment with the missing bit of info.
I like your car...I like the aero kit.
My lights are the Depo tail lights that Del Ray Customs also sell. The resistors were already installed on them so no problems.
My issue was adding the LED 3rd brake light too. The ones I got did not have resistors so I am wondering, when you got yours, do you remember where the resistors were installed (i.e.-double sided mounting tape to the back of the housing)?
Thanks.
Yes they do. That was my thinking the same thing too.
So, with both the normal recessed 3rd brake light and the one in the spoiler, I would need one each, correct?
Also, suggestions on mounting the resistor, especially for the spoiler 3rd light would be appreciated.
I've already given my answer in post #22 and hopefully you found the what you need. My info is from checking the actual wiring in the '99 wiring diagram.
There's a spoiler motor driven switch that directs the power to either the normal 3rd brake light or the spoiler brake light depending on whether the spoiler is raised. So one and only one of the 3rd brake lights will be ON when you press the brake pedal.
If both 3rd brake lights were replaced by LED, all you need is to wire a 6~8 ohm 50w resistor in parallel to ANY of the brake lights including the rear brake lights. You can mount the resistor inside one of the rear brake light cavities.
If you replaced only one of the 3rd brake lights with LED, you need to wire the resistor ONLY to that LED 3rd brake light.
No problem. Appreciate any help.
Yes, I have installed 2 new LED 3rd brake lights.
Neither had a resistor.
I take it from reading #22 that each will need one...in your opinion, where would you mount it with regards to the spoiler 3rd light?
I guess our writing has crossed again.
I read that you would suggest the cavity where the brake light is recessed. My only concern is that the recess for the spoiler is a plastic like material and the warnings about heat concern me...should I be with the one in the spoiler. Another contributor suggested to mount it to the back of the LED housing since the brake lights are really not on for any extended periods typically with the spoiler up.
I see now. You can try this: just wire one 6 ohm 50w resistor in parallel in one of your DEPO lights, inside the DEPO light cavity. That should solve your problem.
Each of the Depo tail lights already have a 50amp 6 ohm installed.
Not sure of what you are saying...should I add another?
The cruise control issue became apparent with the 3rd brake lights and the one in the recess behind the rear wind screen is easy since the recess is metal and I can use 3M double sided tape.
The issue I am having is once I connect the resistor to the 3rd brake light in the spoiler, where do I 'fix/secure' it...on the inside plastic cavity of the spoiler, behind the LED housing, etc.
Thanks for your continued help.
Yes, I got the all of the above. Since each 3rd brake light (one on the spoiler and one below the rear window) consists of seven 3W bulbs so each has 21W of load, identical to your regular brake light bulb. Therefore, the DME expects to see a total load of 21W x 3 (or 63W) when you press the brake. It doesn't care and can't tell where the 63W comes from since all the bulbs/resistors are wired on the same circuit. With only the DEPO built-in resistors, the load is closer to 42W therefore you need to add ONE 6 ohm resistor to load the circuit to make the total load closer to 63W.
Try that first. It won't damage anything (as long as you wire it correctly) even if it doesn't work so no worries there.
I do not remember a resistor being mounted on the 3rd brake light bar. I believe the resistors in the tail lights were enough to warrant not requiring one for the 3rd light. I'm not 100% sure though.
This is normally the case in most situations, however some lights (Spyder branded ones in particular) had some reverse polarity issues before IIRC. I'm running LED tails without any issues and I don't have any resistors in the LED 3rd brake light either.
Thank you. Good idea. You are wealth of knowledge...and with that being said...
Would you happen to know which (color) wire is the positive/hot brake wire and which is the ground that I would tap into to run the resistor parallel?
My car is a '99 996 C2.
It's easy when you have the wiring diagram
There should be 3 wires connected to the stop light socket. The black wire is the positive for the stop light and the brown wire is the ground. The red wire is the positive for the rear side marker (which you should ignore). So you can just wire the resistor on the black and brown wires to test it.
Did you make sure you didn't blow any fuses and the small connector is connected with the right polarity?
Seems weird you would have this issue on a '99.
I think you are thinking of the Spyder style tail lights which require you to use the factory harness. The DEPO lights are truly plug and play...it has the single 6 pin connector.
I checked the fuse which is a 15w located at B-7 which is labeled 'brake light/cruise control' and it is just fine...brake light works fine too.
I think the issue is the resistance...on the Spyder lights you are alluding to, you use the conventional incandescent brake lights from the original lights...the DEPO is 100% LED which make the resistance fall too low...
That is my take.
So, I just need to know, from the rear tail light harness six pin connector coming from the body of the car, which of those 2 I need to bridge with the resistor...it would need to be the power for the brake lights and the neutral.
Ahsai
Thanks for your continued help.
I think the colors of the wires you identified are the colors from the tail light assembly harness....with the new lights, there is a built in harness. So I was thinking of running the parallel resistor across the ground and power for the brake lights somewhere between the body and the 6 pin connector.
With the diagram, would you know the color of the wires or pin locations of which of the 2 of the possible 6 pins I would need to bridge?
Thanks again...
On the 6 pin connector on the car side, the Black/Orange (pin 4) is the +12v for the brake light and the brown is the ground for the brake light (and for all the other lights too).
'YOU DA MAN'
Got home and pulled the DEPO LED tail lights. Put the OEMs in and went for a test drive. Cruise was working again....so we know for sure it was the LED tail lights.
So, I had 50w 6ohm reistors on hand. I pulled the lights and as in videos posted by Delray Customs, rather than have it dangling or attached to the plastic housing, spliced the sleeve around the six wire harness to make a one inch gap about 4 inches from the grommet. Pulled the orange/black tail light positive and the brown ground that YOU pointed out to me and ran them parallel. I mounted them on the back of the cavity near the other factory resistor that came with the DEPOs (presumably the one for the blinkers to prevent hyper blinking)---Did same on both sides (x2).
Just came back and my cruise is working again!
Thanks for your insight.
Perhaps it is a '99 thing because the DME changed from '99 (first year of production in US although in Europe I understand that it was actually introduced in '98) to the later models. The cruise system is presumably different to later models in that my throttle is not electronic as they introduced on the Turbo and then later years (drive by wire vs. e-gas). Perhaps that system on my '99 is more sensitive to the resistance....
Reading some of your earlier posts, 50w on both sides may be 100w total which is more than the 63w needed to equal the three brake lights. Overkill?
Thanks again...saved me a trip to the shop...
Hi all, want to add to this older thread as I think my issue is related....namely, I've upgraded my factory tail lamps and both 3rd brake lamps to LEDs. Never had a problem with the LED tail lamps or the deck LED 3rd brake lamp but could not get the spoiler LED lamp to work. The original lamp does work well however. So, I added 2-50w resistors to the tail lamp wiring but the LED spoiler lamp still won't light.
Can anyone suggest why?
I'm sorry to necropost this but I'd rather revive than create a new thread. I think that brake light issue narrowed down what I've experienced with my (retrofitted) cruise control on my 1998 996 (servo CC unit). It works and I can set the speed, release on manual switching, or clutch / brake switch.
However, I went for a road trip yesterday and noticed the loss of the CC while on the highway while I was expecting to be able to use it (which is the reason why I spent the massive amount of time to retrofit the CC unit).
After a few stops on rest areas and a few tries, I noticed that it was linked to the spoiler being extended, even if I wasn't driving (I have also a in-dash spoiler control + indicator). When it goes extended, as soon as it seems to be seen as "in extended position", the green light of the CC (instrument cluster) vanishes and will not come back even after retracting the spoiler (I have to turn the key off then on again).
My car also got modded (previous owner) by TechArt and has tail lights with leds (and proper resistors). I don't know if the second (spoiler) 3rd-stop-light has been converted but would that spoiler extended switch (humschalter HMS, drive spoiler block, wiring diagram 97 page 65 of the wiring PDF) be responsible of this ?
Missing resistor in the spoiler stop switch ? Just fetching advice before I take this apart.
the weird thing is that the problem occurs even without pressing on the brakes, but only when switching the power source to the 3rd brake light (it seems) in the spoiler system. Would the DME (or something else) would notice an issue in the spoiler stop light and disable the CC unit ? how would it do that ? via the instrument cluster pin (diagnostic pin) ?
thanks
A follow up to my own post in the case it helps others : Looking at the schematic / electrical wiring diagram of the car, the two third brake lights are linked and are also monitored by the car control unit. If a failure is found in the strop / brake lights, you aren't allowed to use the cruise control, which makes sense.
It ended that :
- my new LED replacement of the spoiler brake light didn't have a load and while the circuit between the 2 lights (car and spoiler) was ok, the spoiler one was considered as dead. I managed to retrofit a power resistor, just like it's done on most LED lights conversion.
On my '03 996, I simply replaced each of the brake lights, tail lights, backup lights and the seven bulbs in the center high mount light fixture with individual bulbs that I bought either from
www.superbrightleds.com
or temu. I also replaced the flasher and had no problems with any hyper flashing or anything else. Plug and play. I'm not sure this helps you, but I'm just pointing out that even without the electronic flasher, it all worked without adding resistors.
This is a source reference. Confirm exact model applicability in the original material.
