AUDI A3 Brake Lights on not a faulty switch

[glaisdale101]

My 2004 a3 1.9tdi has a problem with the rear brake lights stuck on(heater plug light flashing),i've tried four new switches fitted by myself and an audi tech,its been on the Vag.com and shows switch t be fine and the brake pedal operation ok as well.No other error codes other than implausable signal from brake switch PO571.The tech guy reckons it a break in the wiring going to earth!
Where do I start! any clues or past experiences welcome.
P.S i've taken out brake light bulbs and replaced,no difference.

[Tame Technician]

Isnt the brake light switch in the master cylinder on that car?

[Tame Technician]

You might find there is a brake pedal position sensor and a switch, if one says different to the other the code, implorsable signal is logged.

You can also get the implorsable signal fault when the brake pressure sensor is faulty, but that should have nothing to do with the brake lights.

You are fitting the switch correctly arnt you, I once had the same problem with a clutch pedal switch, i was on the 3rd one before I got it right.

[glaisdale101]

thanks for your comments,the brake pedal switch is on the pedal and there is no sensor on this model A3 2004 1.9Tdi,so I at a loss as to what action to take next other than to strip the car and trace wiring harness
The switch has been fitted by me and then an Audi tech

Edited by glaisdale101 on Thursday 11th March 12:00

[cpas]

Has it got Brake Assist or similar? On some vehicles, this system uses a different switch with 2 sets of contacts but I'm not sure if it does on Audis. Worth looking into though!

[glaisdale101]

I dont think it has brake assist,but this would have shown as faulty on the Vag test you would have thought

[glaisdale101]

I 've had a look and found that a fuse in the fuse box near battery (n/s) number F7 5amp fuse has blown and when replaced the brake lights work momentarily then the fuse blows again,does anyone know what circuit this may be.2004 audi a3 1.9Tdi

[deck1lion]

i have the same fault did you find a fix i suspect the fuse box