Power door locks on 1998 Ford f350 Pickup

My truck is a Ford F350 crew cab 4 door. My power door locks will not open or close from the master switch on the drivers side.

They will lock from the passenger side, but not open. It seems that they are opening slower and weaker that when the truck was new.

If there is a problem with the master switch, is there is way to test it. Perhaps there is a schematic of the lock switch.

Thank you very much.