Homeowners main floor guest bathroom shower was not getting hot. The shower would have low pressure on the hot side. Gave price to replace the cartridge. Shut water off at the main and drained system down. Removed shower handle and cover plate. Removed the failed cartridge and applied valve grease to the new cartridge and valve. Installed and turned water on. Purged air from the system and tested the shower and the shower now gets hot water. Everything is working properly at this time.