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  • 1993 2.0e Coupe ABS light constantly on...

    I'm hoping someone can help me,

    My coupe was laid up in the garage for a few months and the battery went flat, I charged it up and fitted it and the car fired up fine etc but, my ABS light has been on constantly ever since.

    I've read a thread on here where someone stated that the light comes on with the ignition and the battery turns it out, if the battery isn't strong enough it won't do it.

    It makes sense to me as the light was out prior to the battery going flat but I've not seen anything else to back this up, my battery is showing 12.4v at present and I've read that anything under 12.6v is a sign that the battery is u/s.

    Has anyone had experience of this before? The car never turned a wheel when the battery went flat so I'm inclined to think it's nothing to do with sensors.

    Pete

  • #2
    What volts have you got with engine running? Have you driven the car since?

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    • #3
      Hi, it was showing 12.2v when running. I've tested all the sensors today and they're showing 1200 ohms, I've replaced the relays on the abs pump which made no difference and cleaned the earths.

      I've got power upto the relay by the abs ecu but I couldn't get any power from the plug for the abs ecu, I was only using a test light though but that proved power to the relay.

      The fuse in the top of the relay is good as is fuse 31.

      I think it's the relay next to the abs ecu that's gone but I don't know how to test a relay if it's even possible?

      I've stripped the switch on the dash too and cleaned that up as it was slightly damp, I have a new one on route to me as we speak.

      I'm genuinely stumped now, electrics aren't my best subject but to me it's pointing to the abs ecu relay??

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      • #4
        Forgive me with what will sound like a stupid reply but have you driven the car? I agree with Monkeymagic's question. My S2 spends a lot of time sat up in my garage and sometimes it can take a few miles to get battery voltage up. Occasionally my ABS lamp takes a minute to go out. Maybe there's crud in the pick up rings in your hubs?

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        • #5
          I've done about 2-300 mile since the light came on, it's been a constant since I've started using it. The light came on without a wheel turning when it was in the garage.

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          • #6
            If you have 12 volt at the battery terminals then you have a faulty alternator.
            I would expect battery light to be on though. A low voltage will cause things like abs to have a wobble.
            you should see 14.5 at battery terminerals with a healthy alternator.

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            • #7
              Makes sense, can I check a bad alternator? It looks relatively new

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              • #8
                Just checked the alternator with the car running, heater on full, stereo on and lights on and got 13.8v.

                I think the alternator is fine from that reading, I'm wondering if my issue is a bad abs ecu or that ecu relay 76?

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                • #9
                  13.8 with all that load is about right so as you say I doubt the alternator is at fault. However ABS senders do just go bad without the car moving, it's happen to me before now,to check unplug each sensor's two pin plug and test the resistance with a multimeter. I can't remember off the top of my head what their supposed to be but if one's duff it will be a wildly different reading to the rest.

                  Maybe a daft question but have you tried disconnecting the battery and leaving the car for couple of hours before reconnecting, ie turn it off and on again?
                  1989 B3 2.0 3A 80 quattro... Budget 1.8T Project.
                  1992 C4 100 2.8 Avant quattro... Mobile Sitting Room.
                  1995 RS2... MTM K26/7 380 BHP Conversion.
                  1990 Corrado G60... Breaking For Parts.

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                  • #10
                    I've tested the continuity on the sensors and all were around 1200ohms. None were wildly different.

                    I can only think I've picked some dirt up on the abs sensors when changing springs as I think it was around this time it happened.

                    I've gone and ordered a used relay 76 as I have power to this relay then no power at the abs ecu after this which to me says the relay has gone, but I'm not that good with electrics and was only testing for power with a test light.

                    I'm determined to get to the bottom of it as my retest is up a week today and I've got a baby coming on Wednesday lol

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                    • #11
                      That's a healthy voltage. I would suggest the air gap on one of the abs sensors is wrong

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                      • #12
                        Hopefully over the weekend I'll get chance to prod and poke about underneath the car, if I have a large air gap or dirt on a sensor and I resolve the issue would that extinguish the light automatically?

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                        • #13
                          I've looked at the sensors, the fronts came out easy enough so I cleaned then re inserted them, the rears were too tight though.

                          I got sent this link
                          http://www.isham-research.co.uk/quat...85/abspin.html
                          Which confirmed my first thoughts, that relay 76 the combination relay is duff, I have power upto it but no power at the pump which following the link suggests that relay 76 is U/S.

                          I have one coming to me so hopefully it'll cure my issues and I'll update for others.

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