Shower Diverter in-wall valve question + Cartridge question

[mln]

I apologize if this is a dumb question but I was wondering if someone can explain the function of the two screw valves on the right and left of the attached picture. Are these shut off valves, vertical off / horizontal on? ... they don't seem to do anything when turned?? Thanks.

Second question has to do with the Moen cartridge that I am replacing. I removed an old cartridge, the cylinder pulled out of the outer sleeve initially. I was ultimately able to remove the sleeve as well. I replaced with a new Moen 1200 cartridge and was not able to get hot water, which is what prompted my first question. The pipe to the left of the diverter is warm to the touch, but no hot water regardless of the screw position. Any thoughts on if this is cartridge related? ...is the Moen 1225 cartridge a better replacement option than the 1200?

Thanks in advance for any thoughts.

[jimbo]

the two screws left and right are stops.. They may be multi-turn or ball-type. Your problem may be in the balancing spool above the main cargtridge. I would replace it and the two stops.

[mln]

I'm replying to my own post in case this ends up being of value to anyone down the road. Real plumbers please correct any errors that I might unintentionally include.
I got to a point we're I decided I needed a professional to come in and fix yet another one of my creations. With that state of mind, I threw a little more caution to the wind and found the following:

The screws are shut off valves. They turn more than 90 degrees, they were just sticking and before caution was thrown to the wind I didn't want to push it as I have nothing but bad experiences every time I touch a valve.

The hot water problem was neither the valve nor the Moen Cartridge. With hot water on and cold off, nothing came out of the pipe, while there was hot water in the adjacent sink. I opened the center, large diameter screw. With the large diameter screw removed, there is a small diameter (+/- 1/16") hole on the right and a matching diameter hole at the upper right (+/- 1:00). At a loss, I simply cleaned inside with a wire brush and water started flowing. A little more cleaning resulted in a little more flow, and it was hot water. I can't provide an explanation for what this portion of the diverter assembly is supposed to do, and I am hoping someone smarter than me can explain, but it ended up doing the job and now hot water flows.

Regarding the cartridge, Moen apparently warranty's for life and will provide a replacement if needed. Having no patience however, I bought a 1200 cartridge (brass) and a 1225 (plastic). Tried the 1200 first as it most closely matched the original. It wasn't running hot water very smoothly, instead sort of sputtered. I tried the 1225 and it works fine.

[mln]

Thanks Jimbo. Must have been typing my second post while you were kind enough to reply to my first. If you have a minute to explain how the balancing spool works, and if my follow up post makes sense with regard to cleaning it, I'd appreciate it.

Thanks again.

[jimbo]

A balancing spool is literally that...a spool that moves back and forth and when it moves, it allows more or less water from hot or cold.

In "normal" operation, there is equal pressure on the hot water inlet and the cold water inlet. You adjust the main handle to give you the temperature you want in the shower. Now, especially in an older house, someone flushes the toilet. This causes a momentary drop in cold water flow...and you can get scalded in the shower. A balancing spool moves in response to that drop in cold pressure, and reduces the hot water flow, maintaining a more or less constant temperature to the shower head.

If the spool stick, which they do, the "normal" water flow is affected. Sometimes, you can clean and lube, but when it is older is is just easier to replace the spool.

[hj]

The "balancing spool" is usually attached to that 'hexagonal cap" and comes out when you unscrew it. Unfortunately, most Moen balancers break and you have to extract the broken piece from the valve body, then insert a new complete unit and tighten it in place.