hi velocity, i have checked the AC voltage of each sensor at the connect while rotating the wheel at 1 revolution per second. the voltmeter we have has a 2 vac setting. the rear sensors read 0.1 vac each. the front left sensor was 0.03 vac. the front right sensor had no output. we changed the front right sensor and the output of this sensor was 0.02 vac. the light now stays out. when you are comin to a stop there is a small rattlin noise from the abs. we will buy 2 second hand sensors to replace the ones with low readings, and hopefully this will fix it fully.
thanks to everyone for their comments and suggestions on fixing the abs, peter