Please help! brake lights stuck on, fuse blowing! a3 2.0 tdi 2004 8p

chrisy t

Registered User
Hi guys, got a similar thread on here already but this is just regarding my brake lights. I recently had the coil symbol come up on the dash and my brake lights stuck on, even when i turned the car off the brake lights would stay on, however i ran a scan through vcds and it came up with implausable signal brake switch, so i got a new switch and fitted it and still the same thing, its only about 2 hours ago i went out to the car because it was doing my head in, i went into the engine bay and noticed that the fuse for the brake switch had blown, i changed the 5 amp fuse and put a 10 amp in and as soon as i changed it and turned the car on, it blew again! Could it be that i have a faulty brake switch? Would the fuse keep blowing if the switch was faulty or have i got a serious problem on my hands? Has anybody experienced this? Basicly my audi is out of bounds because i cant drive it with the brake lights stuck on, Would really appreciate it if somebody could help me.

Cheers
Chris
 

paddy

Registered User
What is the fault code. ?
Is it the brake lights on the car and the brake warning on the dash ?
If you take the bulbs out does it still blow the fuse ?
Are you getting a fault code for ABS ( pump?)
Have you tried blocks with VCDS ( around 60-66 from memory ?)
 
Last edited:

mike foster

Fossie
VCDS Map User
Take the brake switch out altogether and see if the lights are still on. If they are then you have a short somewhere. If not then clear the fault with VCDS and try again.

Never put a higher value fuse in a circuit than the designed rating, it can cause the wiring to catch fire.

​Sorry to say this but if you do not have electrical knowledge (and I assume because of the fuse thing that you haven't) then you should get the car to an expert for fixing.
 

chrisy t

Registered User
I toake your point onboard Mike, cheers, i know i do know a little about the electrics, i also know that you shouldnt use a higher fuse, it was the only one i had and i didnt expect the fuse to blow because i was certain it was the switch, coil light is flashing on the dash, When i plug the switch out the brake lights turn off which i think is a good sign! I have a new swithc now, its the newer one that replaced the old finicky one! i will replace the fuse along with the swith tomorrow and see if it fixes it. Thanks for the advice also paddy, if the swithc doesnt work i will try taking out the bulbs, i have got a fault for rear right wheel sensor for the ABS AND ESP also, about a week ago both lights, ESP AND ABS were on my dash, fault was rear right wheel sensor intermittent.
 

ub7rm

Registered User
I presume Audi use the same type of switch as found on VW's but are you aware that there is a very specific procedure for installing the switch? Failing to follow the procedure will damage the switch and it will either not work at all or fail in the on position.

iirc its as follows:

Remove the old switch
Push the brake pedal down to the floor, start the engine if you need servo assistance.
Make sure the plunger is fully extened on the new switch and place it in the bracket but DONT LOCK IT IN POSITION
Slowly bring the brake pedal up, keep holding the switch in position.
Once the brake pedal is fully up twist the switch to lock it into position. Make sure there is a loud click, there is a fair amount of resistance just before the click.
Connect the wiring.

Job done.

Sounds simple but if you just twist it without letting the brake pedal come up against the fully extended plunger you will break the switch internally. Allowing the pedal to come up against the plunger sets the 'off' position of the switch and twisting it till the click locks this in place.
 

chrisy t

Registered User
i have fitted the new switch today and i have now realised it is not the switch that is the problem, although vagcom says brake switch, everytime i even turn the key once in the ignition the fuse for the brake switch in the engine bay blows, i have gone through 5 fuses today just trying it, it is not the switch that is faulty, anybody any ideas? the brake lights just stay on constantly, here are the fault codes i get when i run a scan:

1 Fault Found:
16955 - Brake Switch (F): Implausible Signal
P0571 - 000 - - - MIL ON
Freeze Frame:
RPM: 0 /min
Torque: -98.0 Nm
Speed: 0.0 km/h
Load: 0.0 %
Voltage: 11.55 V
Bin. Bits: 00000000
Torque: 0.0 Nm
Bin. Bits: 0 00 0

2 Faults Found:
00469 - Infotainment Databus in Single Wire Operation
011 - Open Circuit
Freeze Frame:
Fault Status: 01101011
Fault Priority: 3
Fault Frequency: 1
Reset counter: 33
Mileage: 153063 km
Time Indication: 0
Date: 2012.01.08
Time: 15:01:19

00470 - Combination comfort Databus in Single Wire
011 - Open Circuit
Freeze Frame:
Fault Status: 01101011
Fault Priority: 3
Fault Frequency: 2
Reset counter: 33
Mileage: 153063 km
Time Indication: 0
Date: 2012.01.08
Time: 15:01:20

1 Fault Found:
00929 - LockingModule for Central Locking; Front Passenger Side (F221)
008 - Implausible Sign

2 Faults Found:
00871 - Bass Speaker Front Right (R23)
011 - Open Circuit
Freeze Frame:
Fault Status: 01101011
Fault Priority: 5
Fault Frequency: 1
Reset counter: 33
Mileage: 153063 km
Time Indication: 0
Date: 2012.01.08
Time: 15:02:37

00856 - Radio Antenna
011 - Open Circuit
Freeze Frame:
Fault Status: 01101011
Fault Priority: 5
Fault Frequency: 1
Reset counter: 33
Mileage: 153063 km
Time Indication: 0
Date: 2012.01.08
Time: 15:02:39

2 Faults Found:
00352 - Terminal 30A
011 - Open Circuit - Intermittent
00926 - Terminal 30
011 - Open Circuit - Intermittent

Sorry for the long list, its never ending! i cant drive the car with the brake lights stuck on. PLEASE HELP!
 

paddy

Registered User
I have emailed nige, he might be able to shed a little light on this for you. My guess is you have a short outside the brake light circuit that is causing your problem, hopefully Nige will know what is at fault from your fault codes listed above, the problem is even the wrong wattage bulbs can cause a brake light switch code so its not obvious.
My guess is you are going to need to run blocks to further pin down the problem.
Hopefully Nige will log in later.
 

imac83

Registered User
Hi guys, got a similar thread on here already but this is just regarding my brake lights. I recently had the coil symbol come up on the dash and my brake lights stuck on, even when i turned the car off the brake lights would stay on, however i ran a scan through vcds and it came up with implausable signal brake switch, so i got a new switch and fitted it and still the same thing, its only about 2 hours ago i went out to the car because it was doing my head in, i went into the engine bay and noticed that the fuse for the brake switch had blown, i changed the 5 amp fuse and put a 10 amp in and as soon as i changed it and turned the car on, it blew again! Could it be that i have a faulty brake switch? Would the fuse keep blowing if the switch was faulty or have i got a serious problem on my hands? Has anybody experienced this? Basicly my audi is out of bounds because i cant drive it with the brake lights stuck on, Would really appreciate it if somebody could help me.

Cheers
Chris

Hi Chris I have same problem did you get it fixed and how much plsssss tell me not lots £££££
 

Felix B

Registered User
Having the same problem. Did you ever get to the bottom of this?? Driving me a little crazy. Brake switch fuse is blowing even with both rear lights and the brake light switch fully disconnected. Sounds like a short also... not sure where to start looking!
 

Samsparks

Registered User
Hi Guys ,
Audi A3 2004 1.6 petrol .
I have the same issue where the brake lights stay on when the ignition is switched on and go off when ignition switched off .
Brake light switch is fine .
Fuse no7 (5A) in the under bonnet keeps blowing each time the ignition is switched on and last time after it was replaced , I noticed some smoke by the clutch pedal just before the fuse blew .
Found a wiring diagram which showed the brake and clutch switch sharing same supply .
Disconnected both Blue/Yellow wires at brake light switch and found it was the wire for the clutch switch shorting .
The heavens opened up , so have abandoned till tomorrow.
Hopefully I have a faulty clutch pedal switch or the wiring may of chaffed but will update of my findings .
 

Samsparks

Registered User
All fixed , faulty clutch pedal switch which is fitted to the master cylinder on the bulkhead in the engine bay .
 

Felix B

Registered User
SamSparks. Following your findings I have just unplugged the electrical connector from the clutch pedal switch (had to have my girlfriend do it as I could not fit my hand behind the inlet hose).
Once the connector was unplugged, with the brake pedal sensor still unplugged and a new 5A fuse in no7 I turned on the ignition. Fuse did not blow!!
Re-connected the brake pedal sensor... and I finally have control over my brake lights again!

So clutch pedal switch needs replacing for definite. So glad it is not a short in the wiring.

Do you have any pointers on how to replace this? I have a 2004 1.9 TDI. As I mentioned earlier, I could not get my hand behind the inlet hose to even remove the connector, let alone replace the sensor. I did try removing the inlet hose . However, I believe it is connected to the turbo which from the top side of the engine I could not access. Am I able to jack the car up and remove the hose from the turbo that way? Or am I able to change the sensor from the underside of steering column?

Sorry for all the questions.

Many thanks!
 

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