300E 4matic 1991 - no 4matic light

[justino]

I have a 1991 300E 4matic which has a few faults which may be related, the main one is the 4matic is not operative.

I have noticed that the 4matic light doesn't light up on ignition start up. I also have a low speed ABS fault, and the rear diff locks up at low speed in tight bends, although this only happens after the car has been running for 20 mins or so.

It is possible the faults are linked, eg faulty abs sensor, but this wouldn't explain the 4matic light not lighting up when the ignition is turned on. Through reading the various threads my thoughts are:-

1. Dead 4matic ECU
2. Blown 4matic bulb (does this stop 4matic working?)
3. Faulty OVP - fuses in top are ok
4. Faulty ABS Sensor

Does the 4matic have a seperate fuse?

Any help would be greatly appreciated.

 

[leylandp38]

Hi, I have been trying to troubleshoot my 88 4Matic, maybe we can swap ideas here. First up, is your 4Matic ECU actually plugged in? I have found I get the ABS fail and no 4Matic light if I unplug my 4matic ECU. Despite what people say there is clearly a linkage between the 4matic ECU and ABS on 4matic cars.

The rear diff problem is different, I think I got that once when I engaged my 4Matic using the test lever but the 4matic light didn't go out. Apparently it can stay on and misbehave if there is air in the system, which engaging and disengaging the test lever a few times with the engine running seemed to solve, and the diff problem went away with that.

Also have you looked at http://frejvall.com/frejvall.nsf/pages/4matic.htm?OpenDocument&Click=
for more info? Although brief it is very helpful to understand what the system is doing.

regards

Alistair
--------------
1992 300TE-24
1988 300TE 4Matic
1987 300TE breaking for spares

 

[television]

The ABS sensors in the hubs monitor the speed of each wheel, this info is used by the 4Matic control unit. With luck I can give you more info later this week.
Malcolm