Trac fault light - Page 2 - Rolls-Royce and Bentley Forums
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post #11 of 21 (permalink) Old 03-29-2019, 05:27 PM
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You should contact BOLTON Enginieering in UK, John or Graham.
They are what nobody else is and probably could be as John is working for Crewe for so long time. !
Ask therir opinion if it could be ECU .
Will send their information if reuired.

Continental R. 97
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post #12 of 21 (permalink) Old 03-29-2019, 10:09 PM
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post #13 of 21 (permalink) Old 04-02-2019, 12:45 PM Thread Starter
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Thanks for further advice - I have written to Crewe diagnostics to see what they think - carrying out oscilloscope test this week-end.
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post #14 of 21 (permalink) Old 04-05-2019, 03:50 AM
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How did you find the part and part number? I have the same problem on 97 turbo r.
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post #15 of 21 (permalink) Old 04-05-2019, 01:48 PM Thread Starter
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I have the luxury of being able to pass by Introcar en route to work so they are a mine of information on part numbers etc. FYI the NSF sensor is UT14053PA and the phonic wheel is UR26955. Both Flying Spares and Intro can obtain the parts. The sensor apparently comes from Crewe and they stock the phonic wheels, which I am led to believe are manufactured under the direction of Phantom Motors in Crondall, who are specialists for this era car and particularly the Contineltal R,T,SC etc. Does your fault go away when you press the TRAC button to OFF ?
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post #16 of 21 (permalink) Old 04-07-2019, 02:44 AM
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Yes It does go away when I turn it off. It took me a while to find as the light does not come on most times perhaps because it happens so briefly, but it did on one occasion and that gave me the clue as to the reason. I had the cyl head gaskets replaced at Crondall and asked them at that time about the fault and was told it was to do with the transmission lock up. This I doubted as it locks at about 50 mph. Thanks for that part number. I'm guessing it is the anti lock brake sensor and toothed wheel.
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post #17 of 21 (permalink) Old 04-07-2019, 02:56 AM
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Ridiculous price for that sensor. I might try swapping for a spare I have for BMW, or any other car for that matter as I think they're likely all the same sensor, just different fitting. I have Meyle front brakes (from Mercedes) one tenth the price of Bentley and in my opinion, better, except I had to cut off and transfer the anti squeal backplates.
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post #18 of 21 (permalink) Old 04-07-2019, 04:37 AM
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https://en.wikipedia.org/wiki/Hall_effect_sensor If you look at this link, I'm pretty sure this is all it is.
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post #19 of 21 (permalink) Old 04-09-2019, 01:47 PM Thread Starter
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let me know how you get on with a replacement sensor ( I assume that you will replace both fronts rather than one ). The sensor is the magnetic part and the wheel is simply the make and break, that is why I find it so difficult to imagine why a visually sound wheel could be sending a corrupt wheel speed reading. Much more likely to be the sensor which after 20 years and 70k miles of use and corrosion has every reason to call it a day.


My concern in using another sensor is whether the voltage signal being sent to the management system will be different and thus cause any problems further down the line. I have not carried out the signal test from each wheel to check for consistency as I am travelling but I will let you know of anything interesting shows up.


You are correct that diagnosing that it is the TRACTION CONTROL which causes the jolting is difficult because the light only flashes momentarily- it was only when a passenger spotted the TRAC light flashing that I had the joy of being able to switch it off and returning to a normal ride.


Best of luck and please keep us posted. Having your cylinder head gaskets replaced by Crondall is impressive - I shudder to think what your invoice looked like.
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post #20 of 21 (permalink) Old 04-11-2019, 02:52 AM
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My understanding is that the voltage is proportional to the magnetic field created by the rotating magnets in the wheel.. there may be some amplification of the voltage in different sensors. I am sure it is one of the many parts not made by RR/B but sourced as cheaply as possible. It will likely be a while before I do it because 1 it is too cold for me to work outside right now and 2, I can see little benefit, but it would be better to have it working, so i'll let you all know if I get a result.
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