ABS sensor wierdness

[2manykids]

I have changed one of the front abs sensors when doing a wheel bearing and now when i slow down to almost walking pace on the brakes the abs cuts in just before i come to a halt.Any clues?

[Sam]

Incorrectly mounted/dirty sensor is the most common problem.

[2manykids]

Checked the sensor , properly mounted and clean. Any other ideas, do they need changing in pairs to balance or any other expensive nonsense like that?