I just installed a kit for a Price Pfister 01 series three handle tub & shower unit. All new stems, seats etc. The shower diverter is problematical. At first, it would jam up when both hot & cold water was turned on full blast... nothing would come out, either tub or shower spigot. '52 era house, galvanized plumbing. I have successfully installed kit before.
So I redid the diverter, new nylon washer and seat washers on stem. Now, I have to start with just hot water coming out of tub spigot and not full blast, switch to shower mode, then turn on cold water, and then I can increase water pressure. Otherwise, it jams up in the tub mode, and nothing comes out. If I do not reduce water pressure when switching from shower to tub mode, it also jams up.
The good side effect of the post jamming problem is that now I get a much higher rate or presssure of hot water coming out, whilst before it was almost a trickle.
I am almost at my wits end.
Any suggestions?

Hello, it sounds like the diverter stem is defective, or there is debre in the stem. Take the stem out and check for any possible Debre, and look in the valve body to make sure that the port is clear. I would take the stem back to the supplyer and ask them to replace it. Good luck.

When you had the valve open did you turn on the hot and cold to flush out the supplies and the open valve body. It sounds like you still have some debris left in there. Regards, Tom