Passat 2.0S 2002 Brake Lights and Flat Battery with intermittent ESP / ABS warning light

[tweever]

Just thought I'd share this one with you: Went to start car in the morning and found the battery almost completely flat! Noticed rear brake lights faintly on ! Tried to start car but nothing!! Recharged battery and all seemed ok for a week or two. Just off to bed and checked vehicle (you know how it is with a Passat!!) to find mysteriously both N/S and O/S and hi-level brake lights were on with the car locked and no one inside!!! During the week previous I noticed that when driving, occaisionally the yellow triangle ESP/ABS light would come on and it also felt that the engine lost power until the the throttle pedal was released and depressed!

VW Dealer parts dept seems to think there are known problems with the brake light switch causing all this - so for just £8.81 and 20 mins later I fitted the part all seems good, but time will tell if it's a permanent fix. Latest part no is 1K2945511 RDW which seems to be the latest revision (apears there have been about four versions of this switch! Will monitor for the next week or so.

Maybe its me getting paranoid but when turning on the ignition, 3-4 seconds later I hear a series of fairly loud clicks coming from the relay box in the o/s engine bulkead. Appreciate these are relays and they have to operate but maybe it's just that not noticed it before - maybe the noise has always been there but I noticed it tonight and just wondered if it was completely normal?

Thanks!

[David Horn]

Makes sense. The brake lights are permanently enabled so a faulty switch will leave them on all the time. Because it's a fly-by-wire throttle, the computers will get confused between one signal saying "go" and the other saying "stop".

[tweever]

Dismantled the old switch and a pair of the contacts were slighly black which may have been responsible for a high-resistance fault. Looked at the Haynes manual and it seems the rear brake / stop lamp circuits are hard-wired (as opposed to fly-by-wire logic control) to the brake pedal switch However the switch also sends a +12v signal to the ABS ECU. Maybe something was weird with the switch contact tension where it wasn't breaking the circuit at night when no one was looking!