ABS question

[Bluto]

When I start my car and roll at low speeds the ABS light does not come on. If I get rolling over 20mph the ABS light kicks on.

Just wondering what everyones first thoughts would be.

Thanks

 

[89 black SHO mtx]

sounds like you have a sensor or exciter ring problem at a guess. the best way to tell for sure is to have the codes read. i think (its been awhile since i read the abs codes on a ford that old) you have to drive the car to get the light to come on and then read the codes before you shut it off. the code clears itself every time you turn the key off.