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    1. Member
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      08-26-2016 09:14 AM #1
      I've tried swapping in a new bulb, cleaning the harness, flipping the bulb, etc.. But nothing seems to fix it. It randomly will turn off and then randomly turn back on. It's my second brake light (closer to the hatch). Does anyone have a clue what this could be, or how I can properly troubleshoot/diagnose this irritating problem? Or is there a way to completely disengage the bulb warning system? Because I'm down with that too.

      Thanks.

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    3. 08-26-2016 10:45 AM #2
      Quote Originally Posted by Xymox View Post
      I've tried swapping in a new bulb, cleaning the harness, flipping the bulb, etc.. But nothing seems to fix it. It randomly will turn off and then randomly turn back on. It's my second brake light (closer to the hatch). Does anyone have a clue what this could be, or how I can properly troubleshoot/diagnose this irritating problem? Or is there a way to completely disengage the bulb warning system? Because I'm down with that too.

      Thanks.
      So I'm not expert but I'm guessing there is an issue in the wiring somewhere. If you have a obdII tester you might be able to figure it out. Sorry I can't be of too much help...


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      Last edited by LAXbros32; 08-26-2016 at 11:16 AM.

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      08-26-2016 11:07 AM #3
      Quote Originally Posted by LAXbros32 View Post
      So I'm not expert but I'm guessing there is an issue in the wording somewhere.
      Did you mean wiring? Any reason why this would randomly happen? I did notice I had one of the license plate lights was out and replaced it. Not sure if that had anything to do with this or not. Could the bulb be overheating and turning off and then turning back on once it's cooled down? I haven't a clue.

    5. 08-26-2016 11:18 AM #4
      I don't think there is a circuit that would turn it off because of heat. But my guess is that's unrelated, I think your best bet is to check the wiring harness, test it with an Vag Com or go to advanced auto and have them check it with their OBD2 tool


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      Last edited by LAXbros32; 08-26-2016 at 11:24 AM.

    6. Member
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      08-26-2016 12:02 PM #5
      Quote Originally Posted by LAXbros32 View Post
      I don't think there is a circuit that would turn it off because of heat. But my guess is that's unrelated, I think your best bet is to check the wiring harness, test it with an Vag Com or go to advanced auto and have them check it with their OBD2 tool
      Okay, thank you. It's so randomly turning off and on that my next step is to check the bulb socket. Perhaps it's become loose after 118k miles. I'm hoping it's nothing electrical related that's turning the bulb off/on at random. But you're right, Vag-Com and/or OBD2 read might tell me a little more.

    7. Member JRutter's Avatar
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      08-26-2016 02:29 PM #6
      Did cleaning the harness mean cleaning out the bulb socket? They can get corroded over time. One of my front turn signals gives bulb out every 5-6 months and I have to clean the pin in the harness connector and the bulb socket...
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    8. 08-26-2016 02:31 PM #7
      Quote Originally Posted by JRutter View Post
      Did cleaning the harness mean cleaning out the bulb socket? They can get corroded over time. One of my front turn signals gives bulb out every 5-6 months and I have to clean the pin in the harness connector and the bulb socket...
      ^ also a good idea


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      08-26-2016 02:51 PM #8
      Quote Originally Posted by JRutter View Post
      Did cleaning the harness mean cleaning out the bulb socket? They can get corroded over time. One of my front turn signals gives bulb out every 5-6 months and I have to clean the pin in the harness connector and the bulb socket...
      No, actually. I only cleaned the male and female connectors with an old toothbrush. The bulb socket looked brand new, but maybe I'll go over it with a pencil eraser just to test. Bummer about your front turn signals. That would equally annoy me.

    10. Member JRutter's Avatar
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      08-26-2016 11:24 PM #9
      Hey, just noticed Harrisburg, PA. I grew up right outside the city.
      A VR6 AWD w/ lots of goodies

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      08-27-2016 01:49 PM #10
      Check the electrical pins of the bulb holder and body harness connector to the bulb holder for burnt/corroded contacts.

      What kind of bulb did you put in? A cheapo bulb with brass cap? I ask because most of the time a customer comes to the dealer with a concern about a bulb error after they replaced it themselves, the bulb is kinda cheap or just isn't compatible with the electrical system control module. Replacing the bulb with what we get from VW/Audi usually repairs the problem if electrical contacts are okay. Internal resistance of the cheaper bulbs might be too high or low for the control module, so stick with a little more pricier bulb. I don't have any firsthand experience with use of aftermarket bulbs on circuits with control modules, so I can't say for sure what brands will work in your car. Osram and phillips are the brands I remember seeing on OE bulbs when I replace them.

      Tail lamp bulbs aren't fed full voltage, they are powered by the control module with a duty cycle. Tail lights are turned on/off multiple times per second which averages something like a 45% on time, brake lights will be something like 90%. I don't remember exact figures but they adjust to wear and temperature. This method of operation allows the use of a cheaper single filament bulbs instead of more expensive dual filament bulbs and allows them to last longer since they aren't being maxed out. Using a single filament bulb also allows the bulb holder and body harness wiring to be less complex due to less circuits being needed. Less complexity is cheaper in material costs and allows the use of a lighter components.

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      08-29-2016 09:13 AM #11
      So I *may* have figured out the problem. I don't think I was seating the bulb straight in the bulb holder. When I turned the entire bulb housing vertically and looked at it from the side I noticed the one bulb (the problem bulb/socket) was slightly angled to the side. I believe this was causing the bulb to move back and fourth causing the light to intermediately turn off/on. I carefully re-seated the bulb on Friday and I haven't had any issues. Another issue that likely caused the bulb to become lose and angled in the first place was the screw on the back of the housing not being tightened to it's fullest.

      I'll keep an eye on it and report back if anything persists. Thanks for the help, guys.

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      08-29-2016 09:14 AM #12
      Quote Originally Posted by JRutter View Post
      Hey, just noticed Harrisburg, PA. I grew up right outside the city.
      Yeah? How's living in the PACNW? You been there long? I've been wanting to move to Oregon/Washington for years.

    14. Member
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      08-30-2016 09:02 AM #13
      Eh, never mind, it's back. @#$%ing car.

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      08-30-2016 01:17 PM #14
      Quote Originally Posted by Audi_Mechanic View Post
      Check the electrical pins of the bulb holder and body harness connector to the bulb holder for burnt/corroded contacts.

      What kind of bulb did you put in? A cheapo bulb with brass cap? I ask because most of the time a customer comes to the dealer with a concern about a bulb error after they replaced it themselves, the bulb is kinda cheap or just isn't compatible with the electrical system control module. Replacing the bulb with what we get from VW/Audi usually repairs the problem if electrical contacts are okay. Internal resistance of the cheaper bulbs might be too high or low for the control module, so stick with a little more pricier bulb. I don't have any firsthand experience with use of aftermarket bulbs on circuits with control modules, so I can't say for sure what brands will work in your car. Osram and phillips are the brands I remember seeing on OE bulbs when I replace them.

      Tail lamp bulbs aren't fed full voltage, they are powered by the control module with a duty cycle. Tail lights are turned on/off multiple times per second which averages something like a 45% on time, brake lights will be something like 90%. I don't remember exact figures but they adjust to wear and temperature. This method of operation allows the use of a cheaper single filament bulbs instead of more expensive dual filament bulbs and allows them to last longer since they aren't being maxed out. Using a single filament bulb also allows the bulb holder and body harness wiring to be less complex due to less circuits being needed. Less complexity is cheaper in material costs and allows the use of a lighter components.
      Now the right most, driver's side bulb (same one I've been having issues with) will not come on whatsoever, no matter how much I play with it. I tried an OEM/German bulb, but still no such luck. Can I use a volt meter to test this? If so, how would I go about doing that? Any other tips before I schedule an appointment at the dealer?

      Thanks again.

      Just came across this: http://www.audiworld.com/forums/audi...alert-2839312/

      EDIT: Noticed one of the bulbs was type 7506 L, and the rest of the bulbs were 7506 LS. I'm not sure if that could be the problem or what, but swapped to all 7506 LS and the light bulb now works?
      Last edited by Xymox; 08-30-2016 at 03:35 PM.

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