ABS Control unit

[quk@isham-research.demon.co.uk (Phil Payne)]

In message <199712221739.JAA07923@sled> steveb@falcon.kla-tencor.com (Steven Buchholz) writes:

> Here again ... '88 5kCSQW
> 
> I've been dealing with a solid on ABS light for a little while now ... 
> so I thought I'd try to resolve it before the trip.  I had already 
> attempted a swap of the power relay from a working car to no avail.  
> Bentley also states that it is important to have the D+ line from the 
> alternator connected.  I confirmed this voltage looks good last night.  
> I checked the resistance of the sensors per Bentley as well ... all 4 
> look good.  The symptom is that when the car is started the ABS OFF 
> light never turns off, so I don't suspect any sensors in any case.  
> I'm getting to the point that I'm thinking its a problem inside the 
> ABS control box.  Has anyone out there delved into one of these?  If 
> so, are there any fuses or other known failure points inside?

On the later cars, the light will not go off if the accelerometer is 
disconnected.  This is a small black unit under the rear seat with an arrow 
pointing in the direction of travel.  The connector is fairly easy to dislodge 
if you have to go under the back seat for anything.  It's 'normally closed', so 
you can pull the connector off and jumper across the contacts to check the 
switch out.

-- 
 Phil Payne
 Committee Member, UK Audi [ur-]quattro Owners Club