hearbear
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| posted on 8/3/12 at 03:28 PM |
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ABS Help
Daughters renault Megane needs the front abs sensors replaced both front bearings went and took them out, got a pair but they have the opposite plug
fitted male instead of female. Can I cut the plug of and joint the cables too use the new sensors. I have cut the plugs of to see but wire colours are
differnt
3.9Ltr SSC Stylus should be fun
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britishtrident
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| posted on 8/3/12 at 04:33 PM |
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If the plugs are different they will be different for a reason. You may find not only the sensors but also the wheel bearings are no compatible
with your ABS system.
ABS systems have change a lot over the last 10 years.
[Edited on 8/3/12 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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coyoteboy
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| posted on 8/3/12 at 06:13 PM |
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Every ABS sensor I've ever met has been a variable reluctance sensor (coil and a magnet). You have to get the correct resistance (depends on the
coil in the sensor), correct number of turns and magnet strength (determines voltage output with any given passing sensor ring), and the correct
polarity (which way round the waveform comes out). If you have an oscilloscope you can fairly happily interchange them with cutters and joins, without
I'd be cautious - it may read as normal until the system is needed in earnest. Worse case scenario it could damage your ABS ECU, best case
it's probably very similar and will work fine but depends what you want to risk.
Personally I'd take them back and get the right ones on a safety critical item. I'm capable of figuring out if they're ok or not but
it wouldn't be worth the hassle and worry for me so my professional advice would be to get the right part.
[Edited on 8/3/12 by coyoteboy]
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britishtrident
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| posted on 8/3/12 at 07:07 PM |
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In the last 12 years vr sensors & toothed wheels have been getting edged out by Hall Effect sensors triggered by ferrro-magnetic rings built
into the wheel bearings.
Very important with these newer types not to try testing by measuring the testing resistance but by testing voltage.
The easiest way to tell which is fitted is to look for toothed rings on the CV joints, if it has toothed rings its is VR type sensors.
With VR sensors the first diagnosis step check the condition of the toothed rings looking for cracks or breaks, then check the condition of the wiring
then do a ressistance check on the sensors. If that turns up nothing undo the plug at the ABS ECU and check for blue-green corrosion of the pins.
Then check continuity back to the wheel sensors.
Checking Hall Effect sensors is a different ball game, here is part the test method I wrote up for Rover 75 & MG ZT owners.
Hall Effect Wheel Sensor DMM Test.
Tools required Digital Multi-Meter, Car Jack.
1.Jack up the car so that the wheel is clear of the ground and can be rotated by hand.
2.Turn ignition and allow ABS system four seconds to complete self-test.
3.Using a Digital Multi Meter (DMM) set to the 20v DC range, connect the negative lead of the meter to a good earth ground on the vehicle body
then check the voltage on the 12v supply wire to the sensor. If a +12v supply is present then the sensor has passed power on self test. If the
+12v supply is not present then it points to a failure in the sensor or the wiring between the sensor and the ABS modulator ECU. Connection problems
due to water ingress by capillary action via the wiring from the front ABS sensor are not unknown on the 75/ZT, see notes in a later section.
4.Now with the meter on the 2v dc range check the voltage on the sensor output wire, expect this to read between approximately +0.6 volts and
+1.7 volts.
5.With the wheel clear of the ground rotate the wheel by hand while checking output voltage which should switch between approximately between
+0.6v and +1.7v when the wheel is rotated.
6.Repeat for each in turn wheel.
Passing this simple test will only show if the wheel sensor is energised and switching in response to movement of the active wheel bearing it will
not indicate if the active wheel bearing is generating plausible signal. As the magnetic ring in the wheel bearing is relatively delicate and the
clearance between the ring and the sensor is critical, failure is relatively common.
An oscilloscope is the only way to check the quality of the signal from a sensor, the output wave form should be examined using an oscilloscope
when the vehicle is being driven on the road.
Oscilloscope Test on Signal from Wheel Sensor
This test is to check the quality of the signal returned to the ABS Modulators ECU by a wheel sensor. Any defect in the wheel bearing magnetic
ring could generate an irregular signal which will fail the plausibility test and toggle the ABS light on as soon as the vehicle speeds exceeds
7mph.
As with the DMM test the measurements are with the ignition on and power on self-test complete, the oscilloscope connected between the the sensor
signal output wire and a good earth the vehicle body.
To obtain meaningful results I would suggest the test is carried out when the vehicle is on the road driven at constant speed.
When the car is being driven the wheel sensor output viewed on an oscilloscope should be a nice regular square wave between a low of +0.6 and
and peak of +1.6v. I would suggest starting with an oscilloscope timebase setting of 0.1 seconds per division.
[Edited on 8/3/12 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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hearbear
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| posted on 8/3/12 at 08:42 PM |
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The sensors are all vr, the ones with the other plug came of a scrapper simillar year same car and appear brand new it was to see if they were
compatable?
3.9Ltr SSC Stylus should be fun
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coyoteboy
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| posted on 9/3/12 at 10:18 AM |
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quote:
Very important with these newer types not to try testing by measuring the testing resistance but by testing voltage.
Interesting, never seen one.
But they'll all be 3 wire which makes them pretty obvious to spot!
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britishtrident
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| posted on 9/3/12 at 10:55 AM |
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quote:
Originally posted by coyoteboy
quote:
Very important with these newer types not to try testing by measuring the testing resistance but by testing voltage.
Interesting, never seen one.
But they'll all be 3 wire which makes them pretty obvious to spot!
Only 2 wire the sensor is basically a switch, the wires are 12v and output, it earths through the signal line.
You have to to do the tests with it connected up, if you don't see a 12v supply it is usually because the sensor has failed power up self
test and the ECU has shutdown the sensor. If not the sensor itself the most common fault is a wheel bearing problem.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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adithorp
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| posted on 9/3/12 at 11:26 AM |
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Also worth checking that whoever replaced the wheel bearings put the new ones in the right way around (with the magnetic ring to the back/sensor).
I've had a couple that customers have had bearings fitted elsewhere and thats been the problem.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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hearbear
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| posted on 9/3/12 at 01:20 PM |
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quote:
Originally posted by adithorp
Also worth checking that whoever replaced the wheel bearings put the new ones in the right way around (with the magnetic ring to the back/sensor).
I've had a couple that customers have had bearings fitted elsewhere and thats been the problem.
The rings are on the new cv joints not part of the bearings.
3.9Ltr SSC Stylus should be fun
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adithorp
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| posted on 9/3/12 at 02:29 PM |
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quote:
Originally posted by hearbear
quote:
Originally posted by adithorp
Also worth checking that whoever replaced the wheel bearings put the new ones in the right way around (with the magnetic ring to the back/sensor).
I've had a couple that customers have had bearings fitted elsewhere and thats been the problem.
The rings are on the new cv joints not part of the bearings.
Sorry, missed the post saying they were VR type.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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