Clever design or odd behaviour?!

horsemanuk · 22nd December 2013, 12:51

I was just doing a couple of bulbs that had gone and I noticed something odd. It's either a really clever design or it's very odd behaviour...

One of the rear lights had gone (passenger side) and the one above it (brake light) was showing. So, with the lights on and the brakes NOT being pressed from the back you could see the tail light on the right and the brake light on the left. This confused the hell out of me because then I suspected the bulb at the top on the right had gone but I couldn't see anything wrong with it.

When I just put a new tail light bulb in, the light at the top went out so now I just have what you'd expect - two tail lights, no brake lights. Is this a clever design so that even when the tail light goes you still have a red light showing at the back, or should I start worrying about my electrics?!

Greeners · 22nd December 2013, 12:52

clever bit of design

chipsceola · 22nd December 2013, 13:13

innovative design, tail light illuminates at double intensity for failed stop light, or stop light illuminates at half intensity for failed tail light, that way you remain legal and safe!

raykay · 22nd December 2013, 13:27

Quote:

Originally Posted by chipsceola

innovative design, tail light illuminates at double intensity for failed stop light, or stop light illuminates at half intensity for failed tail light, that way you remain legal and safe!

Only the brake light intensity is reduced to act as a tail light if it fails, the tail light intensity cannot be increased to act as a brake light.

horsemanuk · 22nd December 2013, 15:22

That's a good design. I like it. Simple, yet effective.

The brake bulb actually has two filaments to it. As far as I can tell the second filament is purely for this backup reason?

stevestrat · 22nd December 2013, 15:35

Quote:

Originally Posted by horsemanuk

The brake bulb actually has two filaments to it. As far as I can tell the second filament is purely for this backup reason?

Brake light is a single filament 21W bulb, how come yours is dual filament

HarryM1BYT · 22nd December 2013, 15:38

Quote:

Originally Posted by horsemanuk

That's a good design. I like it. Simple, yet effective.

The brake bulb actually has two filaments to it. As far as I can tell the second filament is purely for this backup reason?

The brake lamp is a single 21w filament. To illuminate it dimly as a replacement for a failed tail lamp, the filament is switched on and off rapidly, at a mark space ratio equivalent to the 5w tail lamp (30% ?). When you press the brake pedal it changes to 100% duty cycle and full brightness.

If a brake lamp fails, there is no replacement system for it, the 5w tail bulb can only light to the value of 5w.

ProfDave · 22nd December 2013, 15:42

Quote:

Originally Posted by Greeners

clever bit of design

as he says; good idea really as you get the warning to change the bulb and at the same time are not driving around without tail lights

nice

22nd December 2013, 12:51	#1
horsemanuk Avid contributor Rover 75 Club CDT SE Join Date: Dec 2012 Location: Burntwood Posts: 211 Thanks: 10 Thanked 1 Time in 1 Post	Clever design or odd behaviour?! I was just doing a couple of bulbs that had gone and I noticed something odd. It's either a really clever design or it's very odd behaviour... One of the rear lights had gone (passenger side) and the one above it (brake light) was showing. So, with the lights on and the brakes NOT being pressed from the back you could see the tail light on the right and the brake light on the left. This confused the hell out of me because then I suspected the bulb at the top on the right had gone but I couldn't see anything wrong with it. When I just put a new tail light bulb in, the light at the top went out so now I just have what you'd expect - two tail lights, no brake lights. Is this a clever design so that even when the tail light goes you still have a red light showing at the back, or should I start worrying about my electrics?!

22nd December 2013, 12:52	#2
Greeners Moderator MG-ZTT Join Date: Mar 2007 Location: Ware, Herts Posts: 19,798 Thanks: 161 Thanked 1,249 Times in 1,036 Posts	clever bit of design __________________ *David* Impecunity is the mother of ingenuity Useful how to's for common problems Car Of The Month Jan 2014 [SatNav Power Down] [Coolant Level] [SatNav Repair] [Diesel Non Starting] [Paint Codes] [Rear Light Seals] [Reversing Light Switch] [Bleeding Brakes][Sunroof Drain] [Early ZT's][Instrument Pack Diagnostics][ATC Diagnostics]

22nd December 2013, 13:13	#3
chipsceola This is my second home Jaguar XF 3.0D Join Date: Nov 2010 Location: Southampton Posts: 4,364 Thanks: 119 Thanked 509 Times in 426 Posts	innovative design, tail light illuminates at double intensity for failed stop light, or stop light illuminates at half intensity for failed tail light, that way you remain legal and safe! __________________ Chips

22nd December 2013, 15:22	#5
horsemanuk Avid contributor Rover 75 Club CDT SE Join Date: Dec 2012 Location: Burntwood Posts: 211 Thanks: 10 Thanked 1 Time in 1 Post	That's a good design. I like it. Simple, yet effective. The brake bulb actually has two filaments to it. As far as I can tell the second filament is purely for this backup reason?