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Discussion Starter #1
Hi guys,

I have 300 matic 1990, and I have this problem for a while, whenever I hit almost 80 KM/H the triangle light in the speedometer cluster goes on and doesn't go off unless I press on the brake pedal, or slow down or drive above 120 km/H.

I would appreciate any advice.

Mazin.
 

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The 4matic systems on these cars can be very quirky. My guess is that it is a bad wheel speed sensor. When it comes to 4matic issues, i think it is best to just take her to a good mercedes service shop.
 

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Hi, I have a similar problem, did you solve yours?

1. ABS still pulses before complete stop
2. 4matic kicks in rarely at 15 miles/h and more often when I make a sharp turn
3. 4matic always kicks in with both control units at 45 miles/h ( 60, 70 km/h).
4. Braking always disengages it as it should and function light goes off when vehicle slows down below 35 miles/h
Winter tires are balanced, 25% used and show no defect.
Transfer case is 20,000 miles old and car has 140,000 miles.
And of course when needed the 4 wheel drive is very effective.
Any help appreciated
Thanks
Les
 

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Got it!!

Rust under the right front sensor plate!! Last week I had trusted the Mercedes mechanic to inspect it and had asked him to remove any rust which he said he did. He doesn't seem to understand why a wider gap between the sensor and the teeth of the shaft would lower the voltage from that wheel.
I retested the sensor voltages while driving and tried swapping the right front sensor. I then noticed that there was still rust scales. I removed them with a chisel and both the brakes and 4matic are now functionning properly !
Les
 

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Discussion Starter #6
that's great, I'm happy to hear that, I just wanna make sure you mean the right front speed sensor! and would you tell me what the voltage is supposed to be!

Thanks.
Mazin.
 
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