C4 brothers
-
- Posts: 348
- Joined: 28 Aug 2016, 19:36
- x 20
Re: C4 brothers
Did the cleaning and I use a rag to put the bulb in.
And the right headlight is fine, left keeps blowing.
And the right headlight is fine, left keeps blowing.
-
- Forum Admin Team
- Posts: 41615
- Joined: 15 Sep 2015, 19:38
- x 6765
Re: C4 brothers
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?
Please Don't PM Me For Technical Help
Marc
Marc
-
- Posts: 348
- Joined: 28 Aug 2016, 19:36
- x 20
Re: C4 brothers
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?
-
- Posts: 7445
- Joined: 21 Dec 2015, 13:46
- x 1755
Re: C4 brothers
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.
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.
Chris
-
- Forum Admin Team
- Posts: 41615
- Joined: 15 Sep 2015, 19:38
- x 6765
Re: C4 brothers
There you go then, Chris has nailed the black bulb syndrome in a nutshell 
Please Don't PM Me For Technical Help
Marc
Marc
-
- Posts: 348
- Joined: 28 Aug 2016, 19:36
- x 20
Re: C4 brothers
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.
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.
-
- Posts: 7445
- Joined: 21 Dec 2015, 13:46
- x 1755
Re: C4 brothers
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...'.
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...'.
Chris
-
- Posts: 348
- Joined: 28 Aug 2016, 19:36
- x 20
Re: C4 brothers
Seems logical, too.
Thanks for the info!
Thanks for the info!
-
- Posts: 348
- Joined: 28 Aug 2016, 19:36
- x 20
Re: C4 brothers
12.5V at idle, 13.5V at 2500 rpm.
-
- Posts: 7445
- Joined: 21 Dec 2015, 13:46
- x 1755
-
- Posts: 348
- Joined: 28 Aug 2016, 19:36
- x 20
Re: C4 brothers
Yup, now I'll just hope that it won't go bad again.
-
- Posts: 348
- Joined: 28 Aug 2016, 19:36
- x 20
Re: C4 brothers

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


-
- Donor 2024
- Posts: 4916
- Joined: 17 Nov 2014, 00:36
- x 1467
Re: C4 brothers
That bulb that has turned black looks to have suffered a manufacturing fault.
That's either a slow air lair leak or water contamination (one drop can contaminate thousands of lamps causing them to fail in a matter of hours!).
The water cycle is one of the most dreaded things in incandescent lamp manufacture...
If the lamp isn't properly vacuumed down or has insufficient getter material applied the water breaks down to hydrogen and oxygen in proximity to the hot filament...
2H2O > 2H2 + O2
This free oxygen then goes and oxidises the filament, tungsten oxide is formed.
2W + 3O2 > 2WO3
Because of the high temperature of the filament, this tungsten oxide evaporates from the filament, being deposited on the walls of the bulb.
It gets worse...the hydrogen that was split from the water molecules back at the start is still floating around...this then reduces the tungsten oxide back to tungsten, releasing the oxygen, and forming water again...starting the whole lot again.
WO3 + 3H2 > W + 3H2O
This very quickly eats away at the filament and causes failure. It's crazy how tiny an amount of water it takes to cause problems.
It used to be a particular problem with opal finished lamps which used an internal coating of titanium dioxide as this is really quite difficult to thoroughly outgas properly during the manufacturing process.
There you go... that's your useless bit of trivia for the day.
That's either a slow air lair leak or water contamination (one drop can contaminate thousands of lamps causing them to fail in a matter of hours!).
The water cycle is one of the most dreaded things in incandescent lamp manufacture...
If the lamp isn't properly vacuumed down or has insufficient getter material applied the water breaks down to hydrogen and oxygen in proximity to the hot filament...
2H2O > 2H2 + O2
This free oxygen then goes and oxidises the filament, tungsten oxide is formed.
2W + 3O2 > 2WO3
Because of the high temperature of the filament, this tungsten oxide evaporates from the filament, being deposited on the walls of the bulb.
It gets worse...the hydrogen that was split from the water molecules back at the start is still floating around...this then reduces the tungsten oxide back to tungsten, releasing the oxygen, and forming water again...starting the whole lot again.
WO3 + 3H2 > W + 3H2O
This very quickly eats away at the filament and causes failure. It's crazy how tiny an amount of water it takes to cause problems.
It used to be a particular problem with opal finished lamps which used an internal coating of titanium dioxide as this is really quite difficult to thoroughly outgas properly during the manufacturing process.
There you go... that's your useless bit of trivia for the day.
Current fleet:
07 Volvo V70 SE D5, 88 Renault 25 Monaco, 85 Sinclair C5, 84 Trabant 601S, 75 Rover 3500, 73 AC Model 70.
07 Volvo V70 SE D5, 88 Renault 25 Monaco, 85 Sinclair C5, 84 Trabant 601S, 75 Rover 3500, 73 AC Model 70.