Indefatigable
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- Aug 4, 2006
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Whilst looking on Mercedes Benz Club of America forum site for info about an ABS/4Matic fault that i had with my 1989 300TE 4Matic.175K miles.Please note the word HAD.
A chap called Don gave a reply to an ABS question which gave me the info to test my 300TE.in the reply he stated that the wheel /axle sensors should show a voltage across the terminals of 300mvolts when the wheel was rotated at a speed of one rev per sec.
I had ABS activating at low speed and 4Matic mode 3 ( Rear axle diff lockup)at low speed moving of from stand still.But no wheel slippage.
I extended leads to all 3 sensors up to the driving position and drove at low speed ( on private road ),monitoring the voltage at each sensor,with a digital voltmeter set to 2volt a/c.
1st rear sensor 300+mv (good).then i checked the front only 80-100mv on both( the 4Matic computer reading higher voltage at rear axle=rear wheels spinning go too mode 3. Then under braking conditions ABS computer reading low voltage on front sensors=front wheels locking up,brings in ABS somtimes stoping brake effect completly).The rotors had already been cleaned and both sensors,so this was not the problem.
With the aid of a portable elecric drill i held the sensor close to the open jaws of the chuck and ran the drill( hopeing to simulate the movement of the rotar past the pickup),with this test i got 350/400mv .so i thought that the sensors were o/k.
I did notice that the sensor had to be very close to the rotating chuck to get good voltages.
With this in mind i looked at the opening in the front hub/knuckle were the sensor fits,there was a small amount of corosion(rust) on the top face which the sensor butts upto.With a small rotary file in the same portable drill i cleaned the area,replaced the sensor and spun the wheel. 300+mv on both sensors.
Rebooted the 4Matic fault memory and tested the car.
ABS mended
4Matic mended.
Total cost £00.00
I have only just bought the car about 3weeks ago and the last owner had said that he had just had an ABS fault repaired
The (repair )consisted of removal of ABS warning light bulb,then the removal of the 6 pin relay on top of the ABS unit,dont think thats quite legal ( nice of the person to leave the relay in the glove box )
Hope that the above info might be of help to someone else sometime,as i have seen post of a similar nature before but not with the voltage info.
Good Luck !!
Richard(Moored on the River Trent in a Boat not the Merc.)
Richard.
Location River Trent .Derbyshire UK
A chap called Don gave a reply to an ABS question which gave me the info to test my 300TE.in the reply he stated that the wheel /axle sensors should show a voltage across the terminals of 300mvolts when the wheel was rotated at a speed of one rev per sec.
I had ABS activating at low speed and 4Matic mode 3 ( Rear axle diff lockup)at low speed moving of from stand still.But no wheel slippage.
I extended leads to all 3 sensors up to the driving position and drove at low speed ( on private road ),monitoring the voltage at each sensor,with a digital voltmeter set to 2volt a/c.
1st rear sensor 300+mv (good).then i checked the front only 80-100mv on both( the 4Matic computer reading higher voltage at rear axle=rear wheels spinning go too mode 3. Then under braking conditions ABS computer reading low voltage on front sensors=front wheels locking up,brings in ABS somtimes stoping brake effect completly).The rotors had already been cleaned and both sensors,so this was not the problem.
With the aid of a portable elecric drill i held the sensor close to the open jaws of the chuck and ran the drill( hopeing to simulate the movement of the rotar past the pickup),with this test i got 350/400mv .so i thought that the sensors were o/k.
I did notice that the sensor had to be very close to the rotating chuck to get good voltages.
With this in mind i looked at the opening in the front hub/knuckle were the sensor fits,there was a small amount of corosion(rust) on the top face which the sensor butts upto.With a small rotary file in the same portable drill i cleaned the area,replaced the sensor and spun the wheel. 300+mv on both sensors.
Rebooted the 4Matic fault memory and tested the car.
ABS mended
4Matic mended.
Total cost £00.00
I have only just bought the car about 3weeks ago and the last owner had said that he had just had an ABS fault repaired
The (repair
)consisted of removal of ABS warning light bulb,then the removal of the 6 pin relay on top of the ABS unit,dont think thats quite legal ( nice of the person to leave the relay in the glove box ) Hope that the above info might be of help to someone else sometime,as i have seen post of a similar nature before but not with the voltage info.
Good Luck !!
Richard(Moored on the River Trent in a Boat not the Merc.)
Richard.
Location River Trent .Derbyshire UK
