A4 Brake Warning Light


Registered User
Jan 23, 2012
Reaction score
Hi Guys

Can anbody help with wiring diagram & relay details to cure this problem.
Light comes on after cranking engine,scanned for faults & non showing,have contacted Dealer they say needs relay fitting to cicuit.
Any help would be much appeciated.

Regards Phil
battery on its way out can cause this
As above.

Mine did the same, no faults being thrown (checked with VAS). Changed the battery and its been fine since.
Will test battery just to be sure,but seems to crank over well.
Does the reservoir have the 2 prongs inside like the coolant version?

If so, scratch the surface of the 2 prongs, these fixes the coolant level sender.
i dont think they do. you can pull the sensor out. but its just a black oblong bit of plastic that slides in from the side, theres a two pin plug to the cars loom.
theres a little float and some mechanism inside the reservoir, never bothered chopping a reservoir up to find out how it works tho.

all i know is ive fitted reservoirs, 8 or 9 in the past 2/3 years.........
im guessing theres a bit of dirt/water in the sensor mech/float thats succeptable to cold for some reason that combinded with the drop in voltage on start up causes it to flash up.
its not just diesels either, fitted one on a fwd red 1.8t, thats the most recent one a couple of weeks ago.
mine had this fault when we bought it - the garage replaced it with one from another A4 they had in but it was still happeing so they had to take it into Audi and have a brand new unit fitted - touch wood its been fault free since.
Thanks for all the replies,will try this during the week and hope cures problem.

Similar threads