Need ABS Help!

Hi, I had a previous post about a problem with the ABS system on my '95 Windstar. I still cannot fix the system. A couple weeks after doing a front brake job (new rotors/pads), the ABS system began engaging during normal braking on dry surfaces. When I couldn't figure things out, I brought the van to a reputable local mechanic. He went all over it, cleaning all the wheel speed sensors, bleeding the system, etc. No luck. Heard thru a tech support service that when there are no faults showing and there is still a problem, these vans can have bad rear wheel speed sensors. Replaced both rear sensors. Still no luck. This is driving me and the mechanic nuts. Any ideas? Thanks for any help you can give. Rich.