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THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCH2001 C4 Left Tail Light Out
Leading reported evidence
Replace bulb today and it's still out
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
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Read evidence and context
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Leading evidence: 'Replace bulb today and it's still out' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check bulb orientation as well' (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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Suggestion
You can also easily remove one 10mm bolt that holds on the taillight to remove it completely to check the taillight side for any corrosion issues and such.
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Suggestion
You can also easily remove one 10mm bolt that holds on the taillight to remove it completely to check the taillight side for any corrosion issues and such.
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Suggestion
After you check the wiring and clean the connectors and pins - With double filament bulbs there is a correct way and an incorrect way to insert the bulb in the bulb holder.
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Suggestion
After you check the wiring and clean the connectors and pins - With double filament bulbs there is a correct way and an incorrect way to insert the bulb in the bulb holder.
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Rennlist: 1 discussions
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Generation: 20261027T022239Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
Hey everyone, just purchased a C4 Carrera Cabriolet the other day. Had my mechanic friend check it out, and the car is really clean. Great service history in the last 5,000 miles - IMS, clutch, waterpump, AOS were done.
I bought it with the left tail light out figuring it's just a bulb. I replaced the bulb today and it's still out. Weird part is the bulb does come on when I hit the brakes, so it's getting power, but the tail light is out once I remove my foot off the brake pedal. Since it's a double filament bulb it's almost as if only one filament is lighting. To be sure I also replaced fuse A4.
Maybe coincidental but I also just noticed the left license plate bulb is not working, and the left rear fog light does not come on also (I know there's no fog light in the right assembly)
Where do I go from here? I need to register it and need it to pass inspection. I'll post pics of the car once I give it a nice detail.
Thanks in advance!
You should see the master connector assembly to the right(passenger side) wiring harness. Once you locate that, try unplugging and inspecting it on both sides. You may wanna try some electrical cleaner and reconnect.
You can also easily remove one 10mm bolt that holds on the taillight to remove it completely to check the taillight side for any corrosion issues and such.
Deoxit is a great product - kind of like WD40 but meant to deal with corrosion on electrical connections. Also, get a screwdriver or a pick and try to "rough up" the connections inside the bulb socket. My S430 left taillight turns intermittent about twice a year. I pull the bulb out, adjust the springy bottom contact, rough up the connections and it works.
Ok, I'll take a look at the passenger side to compare. Super easy to remove the tail lights, so I guess that's a plus. To confirm, when you say "master connector", you mean the harness with the sockets that plug into the housing, correct?
It was starting to get dark last night, so I couldn't really get a good look at it. I just replaced the bulb, saw it didn't work, and started messing with the fuses. My thinking is the bulb wouldn't light up at all when hitting the brake if it was a fuse though.
Thanks for the tip. I'll give it a shot tonight after work. What's weird is that if it wasn't making contact I'd assume it shouldn't light up at all. But the bulb lights up when I tap the brakes. Just doesn't stay on as a "tail light" and it's the same bulb we're talking about - just different filaments inside of it.
Just trying to help out a little. After you check the wiring and clean the connectors and pins - With double filament bulbs there is a correct way and an incorrect way to insert the bulb in the bulb holder. The pins will be offset to mostly prevent this problem, but you can still insert a bulb incorrectly. I've seen instances where someone got the bulb inserted in the bulb holder incorrectly and have exactly the same problem as yours.
The tail light/brake light bulb is type P21/5W and equates to a 1157 bulb (not 1156) or try a 7528 bulb
Thanks guys. I'll check the bulb orientation as well. It went it very smoothly, as in I didn't have to force it or anything. Will report back later tonight.
Success! Comparing the bulb socket to the other side, one of the contact tabs had broken. I managed to pull whatever was left of the tab and fold it onto itself. That raised it high enough that it now makes contact with the bulb, so all is well for now.
Took some patience, needle nose pliers, and a screw driver to push it in and fold it over. From what I researched, the sockets are not available on their own, and one would have to buy the whole tail light harness to fix this otherwise.
Look forward to being a part of the community and contribute to the forum.
Bx: Glad you found and fixed your problem. This seems to be an issue with the design of the center contacts in the sockets. When I got my C4S the mirrors would not adjust. I found the fuse blown(wrong amperage fuse installed...hhhmmm). Replaced fuse tried mirrors-blew fuse. Reviewed circuit and found brake lights on same fuse. Root cause turned out to be the top part of the center contact broken and was rattling around in socket shorting out and blowing fuse. Replace wiring harness which is available and not so expensive.
Thanks for those insights. I never realized the mirrors are on the same circuit. When I bought the car, the right and left mirror controls are backwards. (button switched to the left would control the right mirror, and up = down, left = right).
When I get home tonight I'll try the mirrors again. Maybe now that the tail light is fixed, the mirrors are back to normal.
