:confused:I have a Delta 600 (I believe) shower faucet and I can only get luke warm water out of it. I replaced the seats and the ball assembly and I still have the same problem. I got scalding water out of it right after I replaced it but about 20 seconds into the shower it went tepid. Any help would be greatly appreciated. The shower control is the one with the slot that goes vertical and you lift the knob up to adjust flow and twist left and right to adjust temperature. The little book at Lowe's said it was a series 600.

I have since the original post tried the following:
1) Adjusted the white collar that tightens up the ball against the sats
2) Tried turning the ball towards the hot side to allow further control
3) Replaced the ball & seats
4) Been losing sleep stewing on this & tinkering with it

When you take the faucet apart and take out the little springs and washers do you see any kind of deposits in the hot water side? Shine a light into the faucet while it is apart to see if the hole on the left is plugged with any debris.

Another thing you can do, but you will need help, is while the faucet is apart have someone hold a heavy towel over the faucet and hanging down into the shower, as they are holding the towel you turn the water on for just a couple of seconds to wash out the pipes at the shower. Now put things back together and see if it works.

I did all of the above. There are no deposits in either of the tubes. I probed all three holes with a small screwdriver and they are clear of any debris. I ran the water for a few second as well as pumped the water on and off just to be sure that there wasn't anything inside the valve. I looked into the tubes with a flashlight and the cold water side has a little bit of oxidation but the hot side is clean. The shower has been like this for several years and has been unused all that time. I am new to the situation and doing all I can to try and fix it without having to open up the tile and change the valve. Any other ideas? I appreciate the help.

Since you have done all of the above to the valve itself I am not sure that your problem would be solved by replacing the valve, to me it sounds like the problem could be elsewhere.