Diverter valve the problem? Possible brand of shower components?

[MoHandy]

Hoping for some help in my 1920 home with older wall tile I would like to keep. The problem is with the shower water temperature, non consistent from hot to cold. No problem with the tub spout. Assume it is the diverter? Back of plumb wall is a linen closet with access panel, it looks like it was re-plumed last in the 80's maybe. Have no idea what brand the faucet set is. thoughts on what problem is and how to tackle?
Do I just need to figure out brand and if there is a cartridge that requires replacing?
Are there any manufactures that make a three handle shower set any more of quality.
Thank you in advance
Moriah

 

[Terry]

There is a reason that nobody has installed a three handle faucet in the last forty years. You can't consistently control the temperature.
New valves tend to be single handle, with either pressure balancing, or thermostatic.

That old valve was installed very low. The tub spout is almost in the tub. Normally I have the tub spout at least 4-1/4" on center from the top of the tub.
The valve at least 8" above that, depending on the face plates.
A 1920 home may also have very old pipes, and undersized at that. A repipe may be part of the answer if you chose tho stay with that style of valve.

 

[Sponsor]

 

[MoHandy]

There is a reason that nobody has installed a three handle faucet in the last forty years. You can't consistently control the temperature.
New valves tend to be single handle, with either pressure balancing, or thermostatic.

That old valve was installed very low. The tub spout is almost in the tub. Normally I have the tub spout at least 4-1/4" on center from the top of the tub.
The valve at least 8" above that, depending on the face plates.
A 1920 home may also have very old pipes, and undersized at that. A repipe may be part of the answer if you chose tho stay with that style of valve.

Thanks for the super fast response! While I agree on all your points, I'm hoping to figure out a solution that might get us by for a year or two till we can properly redo it in its entirety properly fixing the dimensions. The waste line was just replaced with a new kitchen directly below (why there's a $ shortage), photos of plumb conditions below. So your opinion is a new shower body and three handle set if I don't want to get into patching tile but with this style not a lot of improvement of temperature consistency?