I can't get any cold water out of faucet in the tub. How can I get the cartridge out to clean it? We have tried everything to get it out and it won't budge.

I suppose you have single handle Moen faucet... If that's the case, than you can buy Moen cartridge removal tool at Home Depot. Also, make sure you removed the "U" pin that holds cartridge inside the body. Otherwise, you won't be able to get it out even with the tool... Good luck... Let us know how you did !

We did take out the pin. We finally got it out but the instructions say it should sound like a spray paint can when you shake it and it doesn't. Is there something we need to do to get it apart and clean it?

When you shake with the cartridge, it should sound like there is a metal ball inside the cartridge - just like when you shake a can of spray-paint. But actually, there is a small piston-like piece of metal, a balancer, that makes your valve pressure balanced. If you cannot hear it moving inside the cartridge than you have mineral build-up inside that prevents piston from sliding from side to side. You can try to dip it in LDC liquid. It can be purchased in food supermarket. Submerge cartridge in the liquid for several minutes. If it won't get loose, than purchase new cartridge. Home Depot sells them for about $15.00.

I will probably need a new one. We have well water that is very hard and it has ruined the cartridge. Is it not covered under the warranty with Moen?

Sure, that may be the case. We usually replace Moen cartridge automatically every time there is a drip or any kind of malfunction. We don't service them. They are relatively inexpensive... Good luck to you !