124 Steering Angle Sensor Question

[brucemillar]

Folks

I am trying to narrow down some niggles on my 300TE 4-Matic.

The car pre-dates STAR.

One of the inputs for the 4-Matic is the Steering Angle Sensor.

Were this to be faulty? Would I expect to get a "blink code" ?
Also would I expect to see any problems with the steering/handling?

I have no blink codes/errors and no handling issues. But...... Today I had a look at the sensor. When I removed the steering wheel, there was a fair amount of graphite dust all over the sensor. I think that this is normal on a 30 year old car. I cleaned this off but then noticed what looks like a "bodged" repair to the sensor case. It has a fair bit of glue holding the case together. I sprayed as much switch cleaner into it as I could and a good amount of muck came out. Did the same with the Intermittent Cruise Control switch (that was really dirty).

I have not been able to test my handiwork yet but, assuming that there is no improvement with the 4-Matic? Can I dismiss the Steering Angle Sensor as a culprit?

 

[grober]

the steering angle sensor N49 connects to the 4matic control unit via 3 wires to pins 7, 17 and 18 of the 4matic control unit N30/3. The official test program makes use of a breakout box to monitor all the lines in and out of the control unit while its operational of course but the lines in question into the control unit are
17 yl/wt and 18 yl/bk pin 7 is br/bk
at the steering angle end
17 is wt 18 is bk 7 is br

for this test ignore pin 7

with a voltmeter on DC volts and positive probe on 18 and negative probe on 17
Ignition: ON
Slowly turn steering wheel from its right stop to (center position ) voltage should go from around -5v to zero at centre position
Slowly turn steering wheel from (centre position) to left stop voltage should go from zero to around +5v

voltage should vary smoothly with steering wheel movement with "no drop outs" or loss of signal.

you might have strip a little insulation [ followed by taping up again of course] of the correct cables to get these readings if there are no convenient access points.

see the 4matic circuit diagram and the model 124 .2 4matic.pdf on testing I sent you

 

[brucemillar]

Graeme

Thank you. I just wondered what the steering angle sensor controls apart from 4-Matic. So that were it not working there would be some indication that is obvious through driving?

Sent from my iPhone using MBClub UK

 

[grober]

It doesn't control anything directly its basically a sensor which feeds information to various ECU's about the steering wheels' position. Its input may also affect/influence/modify actions in units like ASD/ASR units in addition to 4MATIC. If its output were totally absent I'm not sure if that would flag up say an ASR fault or simply be ignored since its a "modifier/refiner" rather than a primary controller??

 

[brucemillar]

Ah

That's where I was thinking. In my mind I was assuming that as it's almost a "kernel" then were it to be missing then something else would complain. We have no errors and no warning lights (yes I have checked all the lights are working ;ˆ))

I hope to be able to test tomorrow if the weather is dry. I scooped out a match box full of graphite powder from in and around there, so fingers crossed. I am thinking the powder is from the reluctor rings and flags.