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Question about brake light bulbs please.....

P

Porschekit

Suzuka
Joined
12 Aug 2014
Messages
1,049
997.1 C4S

I got a warning sign on the dash advising to check the rear left brake light, so I bought new bulbs, from Halfords (checked that they fitted Porsche etc).

After fitting new bulb, the sign stayed on, and after further investigation saw that the left brake light (box) is lit but does not brighten up further (like a high beam) when the brake pedal is pressed.

Any thoughts people? Can it be the bulb, because it is lit? yet doesn't get brighter when the brake is pressed like the right one....or wiring maybe? :dont know:

Thanks....
 
Come on you lot....it's been nearly 24 hrs....there must be somebody with a bit of brake light knowledge... :grin:
 
could be one of 4 things:
1. youve bought the wrong bulb
2. the bulb is faulty
3. youve put the bulb in the wrong way
4. some other electrical glitch

Porsche brake light bulbs are pretty standard, they have 2 filaments, one is the rear light, the other is the brake. First thing is to check visually to make sure youve got 2 filaments (to eliminate number 1), if there are 2, chekc to see that both filaments are intact (to eliminate number 2)
I haven't had to change one yet on a 911, but on other cars it is possible to put them in the wrong way around depending on how good the bulb holder is, perhaps that's happened? This would eliminate number 3.
If non of the above then its number 4 and it gets much more complicated...

:thumbs:
 
Thanks Hertsdriver.....I will give those things a try in the order you listed and see if any of them work......many thanks... :thumb:
 
Brake light doesnt work , you replaced the bulb and it still doesn't work ..

It's not the bulb ... unless it's wrong or fitted wrong .. which i doubt .

You are left with a high resistance in the wiring to that bulb or an open circuit .. its out with the volt meter and check it for a feed then work back from there i'm afraid .

Do you need a diagram ? .. i'm sure i could find something should you wish to fault find .
 
Thanks deMort....standby.... I'm trying to sort something out in the morning after buying two sets of bulbs from Halfords
(both wrongly advised by Halfords :pc: ) then checking with my local OPC who told me "Oh we don't keep bulbs for a car that old, they're all LED's nowadays) :dont know:
I didn't know changing a light bulb could be so complex....I'll keep you posted;
 
lol .. no worries .. i'm here 7-9pm every day .. others that can also help are here more often so i dont always answer a post if its already been answered , i'm not a genius .. but some people here are :worship:
 
if the bulb checks out alright (check by swapping it to the other side) then don't forget they all need 2 connections to work, don't ignore the return (earth) side! Twin element bulbs can earth through the "unpowered element" which will give you a dim bulb.
 
jl-c said:
if the bulb checks out alright (check by swapping it to the other side) then don't forget they all need 2 connections to work, don't ignore the return (earth) side! Twin element bulbs can earth through the "unpowered element" which will give you a dim bulb.
Click to expand...

Thanks deMort and jl-c but I don't speak Electronese...... :grin:

My knowledge of amps, volts and watts is about as good as my knowledge of astro-physics, so if it doesn't plug and play then I call in a man to do it.

Anyway the light-bulb saga continued this weekend and I have found that instead of the correct 12 volt P21/4W bulb, Halfords sold me a 12 volt P21/5W bulb :dont know:

Long story short, I eventually bought the correct bulb and fitted it......and we are back in business....I have brake lights :thumb:

However, a point to note would be that when I fitted the new correct bulb the warning sign still appeared on the dash for several starts and then all of a sudden it went away and all is good. Does the system need a while to reset when it gets a new part?

Thanks to all for the helpful contributions....
 
As with all software .. it can get confused and take a while to do what it should dam well do when i tell it after loading and altering the dam software , recoding and it still ignores me and i kick it and i beat it and ..

Im sorry .. i got a little carried away there :D

Its fixed :thumb:
 
I know what you ean..... :pc: :pc: :pc: :grin:

Thanks for your help.....again :thumb:
 
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