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All the bulbs in my highlevel brake light -

Community Veteran
Posts: 6,586
Thanks: 206
Fixes: 14
Registered: 16-02-2009

All the bulbs in my highlevel brake light -

Have failed at once. I replaced one earlier this year, and replaced the hose that feeds the wash sprayer (its a MK1 Focus).
I noticed last week that none of the lights were on, so removed it today to find ALL the bulbs blown, they are in parallel and no sign of water damage.
Any idea's why they would all blow?
21 REPLIES
TORPC
Grafter
Posts: 5,163
Registered: 08-12-2013

Re: All the bulbs in my highlevel brake light -

Perhaps a short in the cable / connection
Community Veteran
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Registered: 16-02-2009

Re: All the bulbs in my highlevel brake light -

Checked the voltage on the lines, 12V when the brake is pressed, and a short would have blown the fuse not all the bulbs.
Community Veteran
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Registered: 02-08-2007

Re: All the bulbs in my highlevel brake light -

Rectifier in the alternator gone .?
Start your car and put a multimeter across the battery terminals up to 14 volt output then it's not the problem, if it's much higher than that then it will cause your bulbs to burn out quickly.
nanotm
Pro
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Registered: 11-02-2013

Re: All the bulbs in my highlevel brake light -

how hard was the engine revving at the time you last used the brakes, its possible they got over-volted once too often, bearing in mind most alternators kick out 14vdc when breaking hard from a high rpm
just because your paranoid doesn't mean they aren't out to get you
Community Veteran
Posts: 6,586
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Registered: 16-02-2009

Re: All the bulbs in my highlevel brake light -

It runs at about 14.1V when charging, I never rev that high 3-4K is usually the highest I go, too used to having diesels. Mind you the voltage hasn't been checked with a GOOD meter, just a plug in tester.
Community Veteran
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Registered: 27-10-2012

Re: All the bulbs in my highlevel brake light -

Did the bulbs look burnt or just a broken filament?
Community Veteran
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Registered: 02-08-2007

Re: All the bulbs in my highlevel brake light -

I think there are diodes in the alternator which as you know only allow the current to go in one direction so if one or more has blown this would cause the voltage to be much higher, as you say best to get a good multimeter on the job if it's not that then at least you can cross it off the list.
Another cause could be a intermittent short in the wiring but I would have thought a fuse would blow if that was the case.
PowerLee
Rising Star
Posts: 543
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Registered: 12-03-2013

Re: All the bulbs in my highlevel brake light -

A Focus will have SMART charging.
The alternator output is controlled by the PCM ( Powertrain Control Module )
If your trying to fault find on a Ford with SMART charging some research on how the system works is a good idea before getting your hands dirty  Wink
Community Veteran
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Registered: 08-10-2010

Re: All the bulbs in my highlevel brake light -

If you put a new bulb in does it light up? If not I would suggest a break in the wiring. I assume it's a hatchback. I had this in my Ford galaxy, which once I worked out where the problem was priced easy and cheap to fix.
Community Veteran
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Registered: 06-11-2007

Re: All the bulbs in my highlevel brake light -

How about... when "stopped" at traffic lights... or some other hold up....    do you keep your foot on the brake pedal all the time you are waiting? or do you use the hand brake.... If the former,... then it is likely that they have "expired" due to the accumulated time they have been illuminated with your foot !..
Community Veteran
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Registered: 01-08-2007

Re: All the bulbs in my highlevel brake light -

Quote from: shutter
do you keep your foot on the brake pedal all the time you are waiting?

That makes no difference, it's the instant zapping of electricity hitting the filament that causes minute amounts of damage bit by bit not the amount of time the bulb is turned on.
I need a new signature... i'm bored of the old one!
Community Veteran
Posts: 16,862
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Registered: 06-11-2007

Re: All the bulbs in my highlevel brake light -

If they are "filament" type bulbs... it does make a difference.... they have a "finite" life time,  and the number of "hours" they are lit, shortens the life of the filament.... therefore... sitting at traffic lights, or other stop situations, with the foot brake depressed is burning time off the filament life....
Community Veteran
Posts: 6,586
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Registered: 16-02-2009

Re: All the bulbs in my highlevel brake light -

I normally put the handbrake on if I am stopped in traffic.
I will need to check the bulbs, will do when my replacement led's arrive. Will also check the voltage at the same time.
Smart charging was it fitted to Mk1's? I know canbus isn't on the MK1.
Community Veteran
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Registered: 02-08-2007

Re: All the bulbs in my highlevel brake light -

If you know anyone who works on cars they might be able to check the ECU to see if it has recorded any error codes which might give a clue as to what is going on.
The local dealers could do this for you but you need deep pockets.
I would be interested to know how you get on once you finally discover the cause.