Moen tub/ shower control, uneven pressure

I do not get cold water, plenty if hit. Replaced cartridge valve still no cold. I then took out valve, shut off hit water at water heater, turned on, no water came out. But there us plenty coming out at sink. Is there some kind of blockage in the moen control in the wall? What parts should i get or do i beed a new unit? It is 30 years old.
Thanks

A thirty year old non-balanced Moen, the cartridge would not have much affect on water pressure side to side.
If you have the pressure balanced "Moentrol", you may have an issue with the balance spool.

At 30-years old, it's iffy if you have a pressure balanced valve. But, if you do, it is entirely normal to have it shut off when the pressure from both hot AND cold supplies are not present. Under normal circumstances, a momentary drop in pressure on one side would cause a corresponding decrease in flow from the other in an effort to maintain the balance (and therefore the temperature). This is a safety feature mandated on all new valves, and could be on the one you have.

REmove the round trim ring and look at the brass valve body. If you have a large slotted "nut' on the right side, you have a Moentrol valve and the balancing unit is part of that 'nut" and has to be replaced.