[urq] Brake System Failure Warning

[Keith Lloyd]

"Question:
How is this physical possible? I presume the switches are simple 'on/off' 
switches and not 'sensors' like like the oil pressure warning sensor?
I also noticed the bottom switch does sweat a little bit and perhaps the 
connector is filled up with hydraulic fluid after 5 minutes, 'shorting' the 
connector as if it was closed?"

A few thoughts but no BTDT.
Is it possible that your system is losing pressure after running for a few 
minutes? Is there a way to test the pressure? Do you have any switches you 
can swap? If all the wiring works fine it points to switches or whatever 
they are sensitive to - i.e. pressure drop. Is the pump worn out perhaps?

Can't think of anything else yet.
Regards
Keith - off to watch the big game




----- Original Message ----- 
From: "Maurits Jonkergouw" <urquattro at moregraphics.nl>
To: "Audifans" <urq at audifans.com>
Sent: Saturday, June 12, 2010 7:19 PM
Subject: [urq] Brake System Failure Warning


> Hi guys, this time I really don't how to fix this "challenge" lol.
>
>
> Challenge:
> 'Fake' Brake System Failure warnings (voice and idiot light).
>
> Checked:
> A. black/purple connector behind the radio > it was already disconnected.
> B. wires+connectors brake switch > tested OK with dummy switches.
> C. warning switches (bottom) and (side) > tested OK with dummy wires and 
> multimeter.
>
>
> My understanding of the warning system and those switches is this: the 
> side switch will 'close' if the brake accumulator (bomb) would completely 
> lose pressure and the bottom switch will 'close' if the hydraulic pump 
> fails with running engine. Otherwise, both switches are in the 'open' 
> position with running engine only?
>
> To verify the switches, I hooked up dummy wires and a DMM to each switch 
> and test drive the car > both switches stay 'open'.
>
> To verify the wires/connectors, I hooked up 2 dummy switches and test 
> drive the car > manual switch 'open' : no voice warning > manual switch 
> 'close' : voice warning and idiot light.
>
>
> Conclusion:
> I 'faked' the behavior of the switches/connectors and they are working 
> fine during testing, but if I connect the 'real' connectors, the voice 
> warning is triggered after approx. 5 or more minutes of driving...
>
> Question:
> How is this physical possible? I presume the switches are simple 'on/off' 
> switches and not 'sensors' like like the oil pressure warning sensor?
> I also noticed the bottom switch does sweat a little bit and perhaps the 
> connector is filled up with hydraulic fluid after 5 minutes, 'shorting' 
> the connector as if it was closed?
>
> I appreciate your help as always...
>
> Regards,
> Maurits
>
> 1986 quattro GV (rebuilt)
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