My shower was remodeled prior to me purchasing the house, it has one lever that controls the water flow and then a knob that controls the temperature. Well, you can turn that knob as much as you want in any direction and the temperature won't change (luckily it's on a decent temperature).
Unfortunately it does not appear that the valve is some standard brand but seems to be Cifial from the googling I have done so it's not like Home Depot is going to have parts. I think I found a replacement cartridge (see link below) but before I drop $141 I would like to have some sort of idea that the cartridge is the likely culprit.
Does replacing the cartridge sound like the right place to start or is there something else I am not aware of that could be causing this?
https://www.fdsupply.com/item/p099-4256/cifial-cartridges/
Here is a picture of the valve that controls the temperature: