shower no longer gets warm.

[Ralph7]

i have a bathroom with a shower that about 3 years ago no longer gets warm. i replaced the diverter cartridge, and it is exactly the same. i played with the supply valves and it doesnt get warm unless i turn the cold supply completely off. since i replaced the diverter cartridge, it shouldnt be the diverter, right? any one ever seen anything similar?

 

[Matt30]

What brand/model?

 

[Ralph7]

american standard, cartridge is part number 023529-0070A.