Brake Light Questions (Fixed Wing)

Tidying up the small things. I have a fixed spoiler with integrated brake lights and also have replaced the third brake light on the decklid above the convertible top. The light in the spoiler is finnicky and only works when you fiddle with it. The decklid light does not appear to work. I do have a set of aftermarket LED tail lights, but the issue was apparent before switching from the OEM light assemblies. I don't believe that fixed wing wire harness was installed, as I was rooting around the engine compartment and noticed that the spoiler microswitches, as well as the red and black wires near them were just taped together with electrical tape. The left tail light will dimly light based on pressure applied to the decklid. I have also noticed that depressing the microswitches will cause the dim light to turn off. If the same microswitch is depressed and held, then the B7 fuse blows when applying brakes. I'm not near the car right now, but I will be and can provide whatever pictures may be helpful. Thanks again! . EDIT: The tail lights appear to be from Del Ray customs. One last thing the rear fog also doesn't illuminate.

Quick updates. I got all the lights to work without having to depress the trunk lid. I cleaned up the wiring and it appears to have solved all of my issues so far. Prior to cleaning up the wiring I was showing around 5-6 volts at the drivers' rear tail light. Connecting the two bn/blk wires in the trunk inline with the spoiler light caused the tailights to stop glowing and allows the spoiler brake light to work. I did have to depress both microswitches in the trunk, but I have the high mounted stop light working as well.

I was hasty in my assessment of the tail lights. They in fact, still do glow (it is confirmed to be both). Both sides get ~6 volts on the Orange / Black (or is it brown) wire and glow faintly with the ignition on. It wouldn't be a big deal if it were not noticable from behind. I don't believe there is a resistor inline with the brake light socket. The offfending bulb socket has 3 lines and the voltage is produced from the side (which I assume is ground) and the bottom contact nearest the side contact. Any ideas?

Quotes source post: 19572424

I just put a fixed Getty Design pedestal wing on my 03 C4S (today). First, I ran the rear spoiler all the way up, took out the "down" relay (behind the left rear seat), and took the car over 75mph. No faults, and the spoiler stayed up all the time. Then I took off the moveable spoiler, ram mechanism and unplugged the harness (just for now) I got the spoiler fault at 75mph (because the ECU doesn't know the position of the spoiler, actually just the "up" switch, I think) and the third brake light doesn't work (not the one in the spoiler, that is the 4th brake light, which is unplugged) Tomorrow I am going to plug the relay and harness back in, run the "spoiler" (actually just the rams now) down, and try to unplug the motor and keep the harness but remove the ram mechanism. I am sure I will get the spoiler light above 75mph (the car is going to Oahu where the freeway speed limit is 45mph... so not an issue), but I am hoping the 3rd brake light will work (with the spoiler "down") I may have to close the down switch manually. As for YOUR problem, start by disconnecting the deck lid plug (under the right hinge/lift strut), and see if your main brake lights work normally. If they do, you have a wiring fault in the lid harness, if they are still glowing, you have a crossed wire somewhere else. I hope you find the issue. Paul

BTW, there is a HUGE difference between the Bk/Or wire and the Br one. the BK/Or is +12v and the Br is ground. Paul

I mistyped. It was the Bk/Or wire. Can you confirm, if able, whether or not you have voltage on the Bk/Or wire with just the ignition switch on? If it is too much trouble, I understand. I am just looking for a sanity check from another vehicle.

Quotes source post: 19573724

Hi Justin, No, I don't think you should. When I get into the garage today, I will confirm with a DVOM. The BK/OR (OG on the attached diagram) wire is the +12v TO the 4th brake light. (I cut mine yesterday, because I couldn't separate the harness from the spoiler without doing so, someday I will put a small 2 conductor connector there, incase I ever want to put the stock spoiler back on) "I think" It should only have +12v when the brake switch (at the pedal) is activated. According to the attached wiring diagram, it activates the 4th brake light (Stop Light High Mounted) only if the "lift switch" is activated: BK/OG to the 4th brake light, to the BN/BK wire, to the lift switch to the BN wire (ground). I think the "high mounted" stop light is the one on the spoiler and not the one on the body, because the one on the body is not part of the deck lid harness ( although ,"I think" it is connected to the deck lid harness via the BR/OR wire, which is grounded through the "lift switch" "I think" the GY/BN is the ground circuit wire that tells the ECU that the spoiler is extended (and stops the 75mph Spoiler Fault warning) I have not verified any of this with a voltmeter, it is just from following the attached schematic. To anyone reading this, PLEASE do not mention that the electrons actually flow the opposite way (negative to positive). That just confuses people (even though it is true). Paul

FAAAAK! I just spent an hour typing up the "fixed wing" wiring solutions (for spoiler mounted 4th brake lights and body mounted 3rd brake lights) and I got this It is all gone. Where is the "auto saved" version (that keeps popping up???) FAAAAK! too late tonight to start over paul

This is much shorter than what I typed last night... Hey Justin, I checked yesterday, no you should not have voltage at the BK/OR wire with ignition on (unless the brake pedal is pressed) If you do, you have a wiring fault you need to find (well you know that already, something is blowing a fuse, and your brake lights are glowing) I took out my decklid harness and components a few days ago in order to remove the moveable spoiler. Now I am in the process of re-doing the harness, so I get what I want with a fixed spoiler and only the body mounted 3rd brake light. I want the ECU to think the spoiler is always up (so no spoiler fault light), but the body mounted 3rd brake light to work (normally, it works only when the spoiler is down) "right now" I think I am going to cut the GY/BR wire coming from "engine hood wiring loom" plug X23 pos#2, the BR wire from pos#5 and the BR/OR wire from pos#6 and connect them together at the plug. That will tell the ECU that the spoiler is up, and connect the 3rd brake light to a ground source (what the "spoiler switch lifting" does when the spoiler is down) My plan is to remove the "spoiler drive motor" (isolate the wires) and all the lifting mechanism, but leave the "spoiler switch lifting" attached and in the spoiler down position (default?) The "stop light high mounted" wires (BK/OR and BR/BK) have been cut (to remove the spoiler) and I am going to isolate the harness side, to make them inop. The light and the wires to it were removed. red is a cut, green is a connection: If you have a spoiler mounted brake light, you would want the BR/BK wire that comes from the spoiler mounted light (NOT the BK/OR, that will blow a fuse!), to be connected to GND (the BR wire at pos#5) to allow the 4th brake light to work, but don't connect the BR/OR wire at pos#6 to GND (BR wire at pos#5) because that activates the body mounted 3rd brake light. For anyone reading this, I found a discrepancy between the schematic and my factory harness: The wire at pos#11 is listed as RD/BK (engine compartment blower +12v) but mine is just BK Does anyone know where I can source the X23 and the engine compartment fan plugs? I could easily make fixed spoiler harnesses for both the body mounted only and the wing mounted only fixed spoilers (and the "spoiler fault" warning would stay off) Comments/suggestions before I start cutting wires?? Thanks, Paul

The 12-pin plug on the spoiler harness appears to be 996-650-479-40. I *think* the fan plug is 996-652-750-40, it might be 996-650-013-40. For the 12-pin you will need some Amp Junior Power Timer pins (really, that's what they are called). VW sells short wires with these pins pre-crimped on them called repair wires. I don't have those part numbers handy. The 996-652-750-40 uses round bullet connector type pins. I don't have the name or part number for those.

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Thank you! That is a start.

Quotes source post: 19575734

Of course before doing "unproven" theories, check your work! I disconnected the microswitches from the mechanism and checked the existing continuity. I am glad I did! In the static condition, the upper switch (on the schematic) grounds pos#2 (GY/BR wire) (normally closed) and the lower switch grounds pos#4 (GY/GN wire). I also discovered that pos#7 and pos#9 are connected in the loom, and the wire color is not BR/GY but BR/RD I am now NOT going to cut the GY/BR wire or the BR wire (because they are connected), but I am going to connect BR/OR to GND (BR) and cut (open) the pos#4 GY/GN wire. This would be the schematic with the microswitches static (and after 2 cuts and one jumper): Here are the factory configuration wires 7 to 12 6 thru 1 All of them Paul

Justin Browning did you get those brake lights figured out? I did my harness mod today and put the decklid back together. It worked just like it was supposed to! The harness mod tells the ECU that the spoiler is UP all the time (which doesn't cause a fault light) and the 3rd brake light wire is connected to ground (just like when the spoiler is DOWN), So I have a working 3rd brake light and no spoiler fault message over 75mph Here is the (really simple) mod: And the completed harness Paul

Sorry, life got in the way and now I�ll be in Germany for about 2 weeks. When I return I�ll get the lights situated using your posts and report back. Thanks!

I disconnected the trunk harness this morning and still have glowing brake lights. I wonder if the lights themselves are the issue. The OEM I traded them for definitely did not have this problem. Maybe not though. I�ll try to disconnect both tail lights and the harness and see if there is any voltage on the car side. Researching further, I wonder if it is the brake switch. I�ll try that as well to see if there is any possibility of internal shorting. Although with the headlight switch off, the brake switch appears to operate as normal. Then there is the issue of the headlight switch. Maybe there is an issue there, I know it is a potential issue at this age. I hate to shotgun parts at it so I guess I�ll start disconnecting and see what comes up. After the voltage issue gets solved, then onto the correct operation of the third brake light and spoiler brake light.

Quotes source post: 19603888

Welcome home. Yes, get those tail lights figured out first, then get to the 3rd and 4th brake lights. Do you want both of them to come on when you apply the brakes, or just one? (either is possible) LMK if you need guidance, I spent a lot of time with that decklid harness, and think I have it figured out. Paul

I do want both to illuminate. I�ll let you know after this stray voltage affair. Thanks!

I dug into this and found the following: Brake Switch Disconnected - Voltage Present on BK and BK/OR at both Taillights (approx. 7volts, depending on how I held the multimeter). Light Switch Disconnected - Same Trunk Harness Disconnected - Same After disconnecting taillight plugs and confirming solid connections to the wing brake light, I no longer have all the brake lights on with the headlight switch in the non-off position. With the lights turned on and depressing the microswitch that actuates the body mounted third brake light, there is a small amount of current passing through the bulbs (indicated by a faint glow). Both microswitches seem to function properly. Why is there voltage prior to the taillight housing? I have confirmed it is not due to taillights, since they were disconnected on both sides when testing. If there is supposed to be voltage sitting at the taillight with the key on, I'll accept that the resistor in the LED taillights are not quite high enough and the glow is minimal as to not bother me too much. I could not replicate the disabling of cruise control when putting everything back together. Everything at this time appears to work as advertised, with the exception of the slight glow of the LED taillights. Thoughts?

Justin, Chasing down electrical faults is no fun. You are doing what I would do, eliminate obvious potential sources. If that doesn't work, try connecting a buzzer to the problem wires (or have an assistant watch the voltmeter) and systematically pull one fuse at a time. That may help locate the origin of the current. Then to find where those current paths cross (a mouse chewed bundle? a corroded plug? a bad ground connection? ect) The 2 wing microswitches only re-direct the connected wires to the brown central ground wire. Look at the pic I posted of them static (connected but not actuated). If actuating one turns on a light, then you have voltage in the light circuit that is making it's way to ground when you actuate the switch. (and you shouldn't, unless the brake switch is sending current) Keep us posted what you find. Paul

Without overthinking, the socket for the offending module does have 3 contacts, since I believe, that the brake light is a dual filament to allow for illumination with the light switch and additional illumination when the brake pedal is actuated. I am certain the brake switch is not faulty due to no change after disconnecting it. Are we certain that there is not supposed to be voltage, standing by on one portion of the socket, maybe to talk to the cruise module (maybe in the DME) to determine if the brake lights work?

Quotes source post: 19608090

I think you are referring to the tail light itself? Sorry I have no idea, I haven't gotten into that yet (I have only had the car a couple of months) Sometimes a bad ground connection will "push" current through another component connected to the same brown (ground) wire... As I said, chasing down electrical gremlins is no fun...

Necromancing my own thread. Further testing shows: - Key On; Faint glow from both rear light assemblies (left is brighter than the right, if I disconnect the left, right increases in brightness) - Key On, Lights any position but OFF; faint glow from both rear light assemblies, faint glow in body and wing (aftermarket) brake lights - Key Off; No apparent illumination - Key Off, Lights in either left/right parking position; respective rear light assembly illuminates, all other rear lights appear off All lights in rear are LED, including the fixed wing and body mounted brake lights