Wabco ABS Modulator Valve
Tried to bleed brakes and I cannot get any fluid out of the abs modulator valve to the left front caliper only. It is on a 2002 holiday rambler ambassador. The abs modulator valve is a Wabco 478 407 062 0. There is fluid going into it but not out. There is sufficient flow to all other calipers. Is something stuck and how can you verify pump operation? I have checked all fuses and any advice is appreciated. The unit was replaced approx 4 years ago to the tune of $3500 and I really don't want to go there again.
2002 Holiday Rambler Ambassador, His and Hers 2003 Harley Heritage Classics and a dog named Rumbles