I have a trane condensing unit.That had waving head pressure,and would go off on head pressure control(400psi).I split the condenser coil which was plugged,and cleaned out with water.Ran unit again ,and had the same issue.I then recovered the refrigerant,replaced liquid line drier ,and put in new rerigerant.Now the pressures are not waving,but after 45 minutes it slowly climbs to 400psi , and goes off on head.