Moen Château shower faucet not mxing hot/cold after replacing cartridge and flushing
I'm looking for some guidance on what do next... I've already done some research on the forums here to solve my problem and have basically exhausted all current things I know to do.
Problem: Moen Château single handle faucet, circa 1982 (not Positemp - pulls straight out, left for hot, right for cold) stopped mixing hot/cold effectively about a week ago. Cold pressure is fine, hot pressure is a trickle. All other faucets/showers in house have hot water with plenty of pressue (i.e water heater works).
Fixes done already:
1. Shut off water main (my house was not designed well... no access panel to rear of shower faucet, it's behind a wall)
2. Removed old handle, eschucheon plate, and cartridge
3. Felt around inside middle of open faucet for obstructions or sediment... did not find any.
4. Felt around from the valve body from the front to see if there are any stop check valves or balancing valves to adjust/replace... none that I can find
5. Sprayed some Lime A Way inside middle of open faucet and let sit for an hour.
6. Turned water main back on to flush the valve and Lime A Way for 2 minutes while my wife watched... water ran clear very quickly, no real sediment came out, shut water main
7. Replaced cartridge with brand new Moen 1225 (Moen brand, not generic) cartridge, brand new eschucheon plate and handle as well for aesthetics
8. Turned water main back on
9. Shower faucet has the same problem.
Suggestions? Given the lack of access panel from the rear my only other choice that I can think of at this point is to have a plumber replace the faucet valve body entirely from the front which would be an expensive proposition given the amount of tear out and retiling needed.