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ABS FAULT ?? PULL FUSE ??

 
Old 10-31-2008, 10:40 PM
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Brett928S2
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Question ABS FAULT ?? PULL FUSE ??

Hi

My ABS is playing up and turning on the ABS light after driving for around 100 yards...

Until I get time to look at it...if I pull fuse XVII ...will that just stop the abs TRYING TO ACTIVATE? and put me back on normal brakes ?

The ABS light activates after 100 to 200 yards, but until that point my brakes are awful (dangerous)

Once the light has activated and I am back on normal brakes , they are fine ...

So will pulling fuse XVII , stop them trying to activate ??


All the best Brett
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Old 10-31-2008, 11:00 PM
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it sounds like you should leave the fuse in, the ABS light illumination means its off line you should have regular brakes without the benefit of ABS.
Check the sensors.. or better yet what was the last thing you fixed???
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Old 10-31-2008, 11:09 PM
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the flyin' scotsman
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In my ABS issue it was the relay on the CE........2 relays within 3 yrs. I also changed the relays on the pump and valve under the LH front inner tyre cover.

I was burning the front tyres to the cords when the ABS was non functional.
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Old 10-31-2008, 11:15 PM
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Brett928S2
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Originally Posted by Mrmerlin View Post
it sounds like you should leave the fuse in, the ABS light illumination means its off line you should have regular brakes without the benefit of ABS.
Check the sensors.. or better yet what was the last thing you fixed???
Hi

Not fixed anything on the brakes lately....

The problem is that it takes around 100 to 300 yards for the ABS light to activate , which puts me back on normal brakes (which are fine)

During that 100 to 300 yards though...the brakes are awful...the pedal kicks back on me and almost no brakes at all...extremely poor pedal response...

I am going to strip the whole system to see whats wrong, but in the meantime (couple of days) I need to know if pulling fuse XV11 will put me back onto normal brakes....and save the 100 to 300 yards with very iffy brakes ??

All the best Brett
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Old 10-31-2008, 11:31 PM
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try pu;lling the fuse and get ready to use the E brake if you dont get consistant results
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Old 10-31-2008, 11:40 PM
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It may make them better - but they will never be like 'normal' (as in non-ABS) brakes because they are configured differently.

The split front circuits for ABS can give you side to side bias issues (that ABS would cancel out when working) and probably you also have a stronger front bias because again the ABS when active can balance it back out... so its much better to get it fixed - don't drive at 200MPH with non-functional ABS (not that you would right?)

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Old 11-01-2008, 01:40 AM
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The ABS light is coming on with our 'Virginia'. I was going to start with the relay at the CEB and if that doesn't clear it up, I was going to try the relays in the fender well next to the ABS unit. This was the course of action Jim Bailey recommended to me and seems to be fairly easy to try and test.
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Old 11-01-2008, 07:25 AM
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John Speake
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Usually with any of the three relays faulty, the lamp will come on as soon as ingtition is switched on.

Driving a few yards and then getting a light is almost certainly a wheel sensor.

I think your S2 is an MY86 with S4 brakes Brett ? If so you're in luck. The ABS wheel sensor for that MY onwards are still available (I have them in stock). The ABS wheel sensors for 84-86 are NLA.
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Old 11-01-2008, 08:40 AM
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I just experienced the same problem with my '87. I had the sensors cleaned and it cleared the problem up...
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Old 11-01-2008, 09:24 AM
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not only clean the sensors but the signal generators on the hubs. Also check the fenderwells for broken wire connections under the hood and then in the spare tire well
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Old 11-01-2008, 10:13 AM
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Originally Posted by John Speake View Post
Usually with any of the three relays faulty, the lamp will come on as soon as ingtition is switched on.

Driving a few yards and then getting a light is almost certainly a wheel sensor.

I think your S2 is an MY86 with S4 brakes Brett ? If so you're in luck. The ABS wheel sensor for that MY onwards are still available (I have them in stock). The ABS wheel sensors for 84-86 are NLA.
Hi John

Yes mine is an 86 S2 ...with S4 brakes etc...
I will check all the sensors and get back to you John

All the best Brett
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Old 11-01-2008, 11:34 AM
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Originally Posted by John Speake View Post
Usually with any of the three relays faulty, the lamp will come on as soon as ingtition is switched on.

Driving a few yards and then getting a light is almost certainly a wheel sensor.
The ABS issue I had was intermittent. From stone cold, key on after sitting overnight, the ABS warning light didn't come but did after only a few kms. I cleaned all all wheel sensors and hub rings.......no change. I then swapped out the 2 relays under the LH front fender..........no change. I then went back to the CE relay which had changed a few years previous and presto issue resolved.

I'm not sure all 3 relays are inter related but the 2 under the fender were original so 20 YO, could they have possibly affected the new CE relay?

What I do know is that my brakes are now perfect especially with the different bias valve and new rear rotor set up.
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Old 11-01-2008, 11:49 AM
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Originally Posted by the flyin' scotsman View Post
I'm not sure all 3 relays are inter related but the 2 under the fender were original so 20 YO, could they have possibly affected the new CE relay?
No they are essentially unrelated (surprisingly...)

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Old 11-01-2008, 07:06 PM
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On a car with ABS, the best way to disable it is to unplug the wheel speed sensors. That will immediately fault the system (at least a newer system). For the 928 I'm not so sure since it's modulations is 3 generations old, but on newer stuff with two sensors pulled you still get electronic brake force distribution, EBD. That drops pressure in the rear circuit. If you just pull the fuse on an ABS car you will have too much rear pressure. In effect it's the same as totally removing the prop valve on an older car. The hydraulic unit runs higher brake pressure than normal at light applies, and then limits rear pressure builds as total circuit pressure goes up. Pulling the fuse removes that functionality.
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Old 11-01-2008, 10:01 PM
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Originally Posted by Alan View Post
No they are essentially unrelated (surprisingly...)

Alan
Amazing..............the ABS system is somewhat simplistic but the door, sunroof, windows are way out there
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