Moen Late 70's Shower Valve

[RbobD]

My Moen shower valve cartridge seems to be failing. The water changes temperature (gets colder) on its own but there is plenty of hot water in the sink. I removed the escutcheon plate and there are what appears to be shut-offs for the hot and cold water, which is good because it's a multi-unit building without shut-offs for each unit. I tried turning the slotted stem with a screw driver but ut didn't budge. Do I just need a bigger screw driver and a stronger turn?

Does this likely take the 1225 cartridge?

I've attached photos. Thanks for any help!

 

[Breplum]

yes, 1225. but your symptom of temp drift is unrelated. changing cartridge can help with drips or ease of pull only, unless there might be some debris trapped in the cartridge

 

[Sponsor]

 

[GReynolds929]

I have found that 1200/1225 cartridges can be prone to allowing crossover as they age.