trimble ezy guide 500

our ezy guide 500 has hardly reached full accuracy this, ie the satellite symbol is yellow and not green, it still seems accurate enough for spreading grassland, with fields already on it, but will not let me create new fields as accuracy not high enough.
gps source- waas/egnos
gps status- uncorr (3d)
satellites 9 (hdop=1.0)

any suggestions