I have a Hayward Phantom pool cleaner, the function that controls, Top, both or bottom is not working. I replaced the Gear box and switch, but that did not fix the problem, it still just rides on the top surface. What do I replace now the manifold? Scott

Try running the cleaner with the top cover off and the pressure on while you hold it with your hand. If you move the switch back and forth you should see pressure changes in the hoses that attach to the manifold. Check to make sure the hoses are attached and there is no leaking pressure. Even a small leak will have a big effect. Next on to the manifold - it has two pistons, one controls the "turnaround" function and the other controls the dive and surface. The pistons get bound up and don't slide easily in their cylinders. Really it's a serious design flaw - how are the pistons suposed to stay lubricated long term with chlorinated water running through at high pressure?

The manifold can be taken apart and the pistons lubricated with standard pool lube. Take the piston caps off of the ends (very carefully) and lubricate the rubber seals. The piston rods may come loose as they do not secure tightly to the small plastic doors that slide to control water flow in he manifold. In that case, take the manifold apart carefully and be sure to keep the various screws organized - reattach the piston rods. I have done this entire process without disconnecting any rubber hoses. You will definately feel like you are in he weeds when you have this thing completely apart. This is normal!
I have had to do this about once a year to keep my phantoms running. Finally, you may want to take a picture of the innards beforehand to help you remember how the hoses and components fit in the unit. It's confusing. Good luck!