Antilock break system question; with winter approaching I thought about finding a solution for this.

1986 5000 CS (quattro turbo), 'Antilock Off' light on the dashboard turns on whenever driving above 15 mph and remains on until the car is turned off again. Pushing the Antilock Off button on the center console at stoplights causes the dashboard light to turn off, only to turn on again above 15 mph.

I have a replacement ABS pump and a couple of newer wheel speed sensors I could swap for. I'm wondering what component more likely needs to be replaced, or if it's even something simpler such as a fuse.

Thanks.

 

Ammendment:

When the light is off, the ABS system is fully functional and works well on gravel; however, still automatically turns off when going over 15 mph.

 

start with cleaning the wheel speed sensors