quattromike
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 posted on 28/3/06 at 10:12 PM |
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ABS Trouble
Hi all I'm trying to put my old 91j audi 80 quattro back on the road but I can't seem to get the abs sorted out I've had all
the drive shafts out and cleaned off all the toothed bit were the sensors pick up the puls , Ive even changed 2 of the sensors, I know one was knacked
but after I changed that and it still didn't work I changed another one. I've checked all the plugs and drove about unplugging them one at
a time and it did make a difference but with them all plugged in it doesn't play the game
When I start up and drive off a little bit, as soon as I put my foot on the brake lightly or even full force the abs cuts in and chatters like the
wheels have locked up and it's trying to release them , but it ends up not slowing the car down at all
There is a buton on the dash to switch the abs off and when I do this the brakes are ace wil stop every wheel at the same time even on the muddy road
I was on at the time, but as soon as the abs is switched on again it won't brake on any wheel it just cuts in.
I'm trying to get it through an MOT and there is no way it will like this. can any one shine any light on it? pls!
Mike
"At the end of the day, I think it's going to get very dark"
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smart51
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| posted on 29/3/06 at 07:03 AM |
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Have you set the gap right between the toothed rings and the sensors? This is important if the sensors are to work correctly. If the gap is too
large then it wont pick up the signal at low speed.
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SeaBass
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| posted on 29/3/06 at 07:27 AM |
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quote:
Originally posted by CaLviNx
if you can get some info their might be a resistance reading that will allow you to test and see if they are ok, and you could try a multimeter set to
ohms
[Edited on 28/3/06 by CaLviNx]
Unfortunately resistance is unlikely to tell you much with these sensors... If you can get hold of an oscilloscope you could view and output voltage
square wave trace from the sensor when you spin the wheel... Pretty much the only way to check them.
You're probably better asking these sort of questions on Audifans.net the community loosely related to the Audi Owners Club UK... I've
found them a very friendly bunch over there... You'd be best checking out previous posts in the Series 3 chassis section here...
http://www.audifans.net/modules.php?name=Forums&file=viewforum&f=2
I'm also seabass over there!
Thanks
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omega 24 v6
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| posted on 29/3/06 at 10:52 AM |
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Most Abs sensor systems work by measure the induce ac voltage at the wheel speed sensors. Jack up and turn each wheel in turn (watch you dont have an
lsd or such like) and measure the ac voltage at each plug end (preferably at ecu) they should all give roughly the same reading at the same wheel
speeds.
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smart51
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| posted on 29/3/06 at 11:19 AM |
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The voltage generated by the sensors increases with wheel speed. at speeds around 5 km/h, many ABS systems detect no voltage at all.
[Edited on 29-3-2006 by smart51]
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froggy
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| posted on 29/3/06 at 12:06 PM |
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as far as sensors go the usual one to fail is n/s/f followed by n/s/r from bumping up the kerb
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Ketchup
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| posted on 29/3/06 at 12:42 PM |
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have you double checked all the wheel bearings to make sure there is no play as this will upset things, also i have had a wrong sized tyre on one
corner cause a similar problem, the point about checking the gaps between sensor and ring is also a strong posibility, worst case will be the abs ecu
losing its mind
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quattromike
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| posted on 29/3/06 at 07:59 PM |
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Ok I've posted on the audi fans .net.
An oscilloscope is not easy to come by, thats what my mate rekons I need to check if the sensors are ok to see if I get a frequency from the wheel
speed sensors when the wheels are spinning.
It could also be the abs ecubut they are not easy to come by either.
Mike
"At the end of the day, I think it's going to get very dark"
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