how to fix husqvarna yth150 lawn tractor?

mower deck will not engage. bought new elect clutch, installed new pto switch, installed new relay switch, mower starts and runs fine but nothing happens when i engage the pto??????? i'm very frustrated!!!! Everything shuts down when i raise from seat also, so i think that is working ok. I just don't know what it could be???? model yth 150 (954140007j)

rjh
August 2011