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Brake pedal sensor 850 1994

posted by  yothere on  Mon Dec 15 02:57 CST 2008
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last visit: Sat Sep 27 10:27 CST 2014
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Good day everyone!

In trying to diagnose a strange shudder I decided to pull the codes off the ABS computer.
I got something telling me about my brake pedal or brake light switch detector. I investigated under the steering column and found two buttons that seemed to detect if I was depressing the brake pedal. The lower of the two (farthest away from the steering wheel) seemed to be connected to a vacuum line and I hypothesize is linked to the cruise control.
The one above this one (closer to the steering wheel) I (again) hypothesize controls the brake lamps at the tail. Is this the switch the ABS is pointing me to?
--
-Hector








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    Brake pedal sensor 850 1994

    posted by  jeza on  Wed Jan 21 13:15 CST 2009
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    last visit: Mon Feb 16 09:43 CST 2009
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    Hello
    I am a recent inheritor of a 95 850 that is occasionally displaying major shuddering upon braking. I have also pulled the code 142 (foot pedal switch) and am wondering if this switch being faulty is enough to cause this problem.

    Yothere, did you ever sort this issue out ? Does anyone else have any info on this ? The intermittent nature makes it very hard to diagnose. Brakes have been checked and all seems ok.Does seem to occur on hot days in hilly terrain when brakes are hot. Not very often, but quite major when it does happen. Through chassis rather than pedal or steering wheel. No ABS light coming on.

    Am bumping this thread as it relates possibly to my issue.

    Can anyone help?








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      Brake pedal sensor 850 1994

      posted by  yothere on  Wed Jan 21 15:15 CST 2009
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      last visit: Sat Sep 27 10:27 CST 2014
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      I cleaned the ABS sensors in front about a month ago and haven't had the problem show up again.

      However, the problem only existed for me on downhills and when it was raining and I haven't had too many of those downhills here in Fl.

      The ABS sensors were quite dirty when I cleaned them, fairly simple to do.

      I'm having the brake pedal switch changed tomorrow as a matter of fact. I told the guys at the shop where the car is what the error was and I hope they test the switch before they change it to see if that is the issue.

      Once I cleaned the ABS sensors the light started coming on more sporadically, whether or not I was depressing the pedal which is very weird.

      If you want, once they replace the sensor, I'll let you know if it pops back up again.

      I see in your post that your shuddering happens when you brake. Mines would happen regardless of whether I was breaking or not. If you've completely ruled out that your rotors aren't a bit warped then your issue may be similar to mines.
      --
      -Hector








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        Brake pedal sensor 850 1994

        posted by  KlausC on  Fri Jan 23 04:49 CST 2009
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        last visit: Fri Oct 24 10:15 CST 2014
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        I apologize for going down the wrong track. The 142 code is a bad brake pedal switch, and the 141 code is for the brake position switch. The former relates to the switch under the steering column, the later refers to the switch in the engine bay
        The 141 is probably caused by a bad plug connection. The position switch is at the center of the brake vacuum canister facing the front of the car. I had one when it got very wet, running through 1-2 inches of water at relatively high speeds. Think autocross and sliding sideways :) :)

        Klaus

        --
        Volvoless. Sold the R. There is now a void...








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    Brake pedal sensor 850 1994

    posted by  KlausC on  Mon Dec 15 04:29 CST 2008
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    last visit: Fri Oct 24 10:15 CST 2014
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    You are correct on both counts. Try not to disturb the CC switch. You should be able to verify the switch not working with a volt meter. There is a plastic push pin that might have worn down, causing the switch to malfunction. Be careful when removing the switch, the plastic tabs get brittle with age.

    Klaus
    --
    Volvoless. Sold the R. There is now a void...








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      Brake pedal sensor 850 1994

      posted by  yothere on  Wed Dec 17 22:55 CST 2008
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      last visit: Sat Sep 27 10:27 CST 2014
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      Thanks Klaus. I reckon I'll try to test it while its still in the car if I can manage. It seems rather difficult to remove, I can't really see what I'm doing because that CC thing is there and I don't want to risk breaking a 14 year old plastic doohickey.
      How do I check to see if it works using a voltmeter. This thing had two connectors so I figure I'm testing for an open circuit but how does one test that using a voltmeter? Resistance?
      It's been a while since I took physics.
      --
      -Hector








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        Brake pedal sensor 850 1994

        posted by  will rehsper on  Thu Dec 18 04:03 CST 2008
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        last visit: Tue Jul 3 14:55 CST 2012
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        Your reluctance to mess with the CC switch is warranted. I've broken one because I didn't really know how it's retained on the bracket. $25 or 30 later I had to be very careful not to break the new one while installing it.

        You're on the right track with the voltmeter. You want it set to read resistance in Ohms. Here's a picture showing the setting you want (except you want it in the 200ohm range, not 20k): http://faq.f650.com/FAQs/Photos/ElecPhotos/OhmmeterOhms.jpg
        When the leads of the meter are touching, the meter should read zero or very close to it.

        -Will







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