C4 brothers

Tell us your ongoing tales and experiences with your French car here. Post pictures of your car here as well.

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Cutac
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Re: C4 brothers

Post by Cutac » 13 Sep 2018, 19:21

Did the cleaning and I use a rag to put the bulb in.
And the right headlight is fine, left keeps blowing.

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GiveMeABreak
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Re: C4 brothers

Post by GiveMeABreak » 13 Sep 2018, 19:35

Right, then I would look at the bulb holder of the left one and the wiring - check all the contacts and the wiring for any shorts. Does the bulb fit squarely in and are the pins making good contact. Has to be electrical if it is happening consistently on one side - or the holder unit. Maybe there is some more corrosion inside the bulb holder unit itself that you can't see?

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Cutac
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Re: C4 brothers

Post by Cutac » 13 Sep 2018, 20:48

I did look at the holder a bit today and I haven't seen anything worrying. I'll measure the voltages tomorrow, which readouts should I get? Is it 12 on both but light intensity is different due to a different filament?

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white exec
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Re: C4 brothers

Post by white exec » 13 Sep 2018, 21:09

Clear tungsten bulbs that become internally blackened are what happens when the tungsten filament evaporates, or burns up, and the vapourised tungsten condenses on the cooler glass, and blackens it.
Cause can either be continual excessive voltage (eg 15v+) or poor quality manufacture (vacuum not complete, allowing combustion of the filament).

Standard 21/5W bulbs are, as said, not suitable for DRLs; not built for continuous use. The 5W side (tail-light intended) may well be ok, but the 21W (typically a brake light) just isn't. LEDs are the way to go.

Voltage at lampholder (engine running at idle, headlights and most other electrics switched off) should be 12 to 12.5 ish. Raise engine revs to 1500-2000, and voltage should not exceed about 14.4v.

Good quality automotive bulbs are rated for continuous use at 14v. Cheap items are sometimes just 12.

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GiveMeABreak
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Re: C4 brothers

Post by GiveMeABreak » 13 Sep 2018, 22:30

There you go then, Chris has nailed the black bulb syndrome in a nutshell 👍

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Cutac
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Re: C4 brothers

Post by Cutac » 13 Sep 2018, 23:51

I'll measure voltages and report.
Original bulbs lasted 6 years, next lasted around half a year and then 2 pairs died in a month. It's not due to 21W filament, it's something else.

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white exec
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Re: C4 brothers

Post by white exec » 14 Sep 2018, 07:43

Also seems (and not particularly a PSA thing) that bulbs fitted by factory when the vehicle was built tend to be of high quality / long life. (The latter can be achieved by using bulbs rated 15/16v, and thus "under-running" them on the car. A 15% voltage reduction (under-run) typically extends bulb life to 400%.). After-market bulbs appear to be different!

This could well be done to avoid bulb failure under warranty, or in the early years. A good bit of PR, as it leaves initial customers with the feeling that 'It hasn't even blown a bulb...'.

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Cutac
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Re: C4 brothers

Post by Cutac » 14 Sep 2018, 12:14

Seems logical, too.
Thanks for the info!

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Cutac
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Re: C4 brothers

Post by Cutac » 14 Sep 2018, 18:31

12.5V at idle, 13.5V at 2500 rpm.

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white exec
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Re: C4 brothers

Post by white exec » 14 Sep 2018, 19:03

Nothing amiss there.

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Cutac
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Re: C4 brothers

Post by Cutac » 14 Sep 2018, 19:15

Yup, now I'll just hope that it won't go bad again.

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Cutac
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Re: C4 brothers

Post by Cutac » 29 Sep 2018, 16:16

Image

And this is something that's bothering me.
Front bumper doesn't sit flush with the fender. Any idea why?
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