I don't beleeeve it!

No, that doesn't explain it at all.

I thought blown bulbs were almost invariably less bright?

[...]

Care to repeat this with the brake lights and let us know the results?

Indeed. Although I've seen American industrial machinery as badly done...

Chris

Cost. In any case, the average driver could always find someone to check for him, if only a passer-by. The fact is, Mr(s) Average doesn't give a toss.

Many modern (ie multi-plexed) cars do test the lamps now.

Chris

The message from David Taylor contains these words:

On many cars it does!

The message from "Paul Hubbard" contains these words:

Or, with modern cars just have a test sequence in the multiplexed wiring controller. Push button while turning key and it'd run through all the lamps in sequence all round the car.

The message from Chris Whelan contains these words:

Ha, my Audi does - and has told me for the last year there's a bulb out

- which there isn't.

Ah, yes you're quite right. I was meaning why the single working bulb on a car with a blown bulb would be brighter than either working bulb on a car without any blown bulbs. But I suspect you knew that... :)

Dontcha just love modern technology......? Not.

PDH

Or as I do, put SWMBO in the car, then stand behind and confuse the neighbours with the following dance (guess the check).

1) Hold out left hand, open and close palm 2) Hold out right hand, open and close palm 3) Lift foot and stamp on ground several times 4) Hold out right hand with fist, pull towards you in a left right zigzag manner 5) Place both hands over eyes 6) Wave both hands in a confused manner as though lost 7) Walk to front and repeat steps 1 and 2 8) Repeat step 5 9) Hold both hands low to waist height 10) Hold both hands high to head height 11) Repeat step 6 (if fitted)

You'll all be doing it on TOTP next week. :o)

PDH

Then try it with dubious connectors, as found in many cars.

I've seen aircraft that badly done...

Umm. It's *exactly* to do with what is being discussed here. What are the possible causes for the observed effect of cars with one tail light out having the other one brighter than normal.

Or had some real life issues with cable sizing, connector resistance, that sort of thing.

Inertia. With a lot of these discussions it gets like talking about Creationism. Somebody decides to believe something with no logical basis then you just can't argue with them. Things have gone that way so often I was frustrated in advance. My apologies. So far.

BTW, don't your bulbs use electrons? mine do. A bulb is an electronic device. Although I'll grant that older, simpler cars could just have 'electrics', something modern like a Citroen C4 is definitely electronic.

Yes, electronics. Thanks for reassuring me. I did an HNC and most of a degree in it, plus half a career.

In the electrical industry, I suspect you were using mostly AC and higher voltages/lower currents. So in low power low voltage DC circuits in poorly maintained conditions I suspect there are aspects of voltage drop that may have escaped you thus far.

The bulbs bulb with monotonous regularity on my wife's Previa. Replacement entails removing the lamp cluster from the car. Two screws which you have to be careful not to lose due their location, and some swearing because the rubber seal is stuck. Not a roadside job if you can help it.

LEDs would be the answer if they were legal (yes I know they are if e-marked, but those are usually only the oe complete units like BMW etc).

I don't understand why bulb failure warnings are not mandatory on brake lights at least - the rest you can check easily, but brake lamps need a partner to assist.

On Tue, 30 May 2006 15:42:29 +0000 (UTC), I waved a wand and this message magically appeared:

Well, my headlights do pulse between dim and normal if both indicators goes on!

On Tue, 30 May 2006 19:49:06 +0100, I waved a wand and this message magically appeared:

On Tue, 30 May 2006 19:39:05 GMT, I waved a wand and this message magically appeared:

Vorsprung durch technik! Ja!

Then there's something wrong with your battery/wiring...

Thing is, none of this will make a bulb brighter than _normal_. It describes how one bulb blowing can make the other bulb brighter than its previous brightness. For that to be possible, both bulbs, when working, must have been dimmer than it was supposed to be. One bulb blowing would merely reduce the current (and thus voltage drop) in the wiring, allowing the remaining bulb to more closely approach its intended brightness.

Surely no one is describing that situation, as when you see a car with a blown bulb, how do you know the original brightness when both bulbs were working?

In which case both bulbs will always be dimmer than normal, but one working bulb will be brighter than two working bulbs.

When seeing someone elses car with a blown bulb, the only reference you have to "normal" is not the other bulbs brightness, but the normal brightness of a headlight. It won't be brighter than that.

[snip]

If you belong to the same era as that little lot, you may be able to remember, as I can, when you could get a kit of fibre optic cables and fittings and connect up to the dash to show when the lights were on. Seemed like a lot of work for little benefit to me.

Steve