the knob is one of those big ones that you pull out then turn left for hot water and right for cold. it was probably made in the 1980's and says its "chateau by moen". its loose and wont get the water warm enough. theres nothing wrong with the hot water heater and all other faucets get the water hot.

I am very home improvement impaired

 

Moen cartridges are guaranteed forever. Often you can just present the old cartridge at a big box store (e.g. Home Depot) or plumbing supply and be handed a new one, no questions asked. Call the particular store to confirm this.

To replace the cartridge you'll need a phillips screwdriver, needlenose pliers, and a little tub of plumber's putty. You'll have to shut off the water at some point but don't yet unless you see easy access to hot and cold shutoffs leading to the shower, perhaps through the wall or under it.

First, pop the cap off the knob with knife, fingernail, whatever, to reveal the screw holding the knob on. Remove the screw, and carefully jiggle the knob off (you know what happens when you pull it). Remove the two screws holding the wall plate, and pull the wall plate away (it may be stubborn with caulk).

Now you can see the works, and if you're lucky there will be accessible shutoffs in there. Otherwise, hunt for the shutoffs - which may not exist - or shut off water to the entire house.

Temporarily re-attach just the knob to test water is off. If you used local shutoffs (I prefer this as it avoids the Plumber's Nightmare of an ancient house shutoff needing service itself because it was disturbed, and it allows people to go on using the rest of the plumbing), then the shower pipe still contains some standing water which will gurgle out, possibly into the wall, as the cartridge is removed. I use a punctured plastic bag and rubber band to direct this water into the tub, but you could devise your own setup. If other fixtures are shut off as well, you can just open one to let that water in the shower pipe drain out.

The cartridge is held in with a horseshoe-shaped clip. Pull the clip up and set aside. At this stage the cartridge has nothing holding it in but corrosion. So rapping on it sometimes helps, but you can probably extract it easily just by screwing the knob back on and pulling on the knob.

Bring it when you get the new one.

Clean out the opening where the cartridge inserts with a twisted paper towel, and put in the new cartridge. The reverse procedure should be obvious now.

Turn the water back on now while a leak would be visible. Check that hot/cold isn't contrary to the knob markings - if backwards take the cartridge out, rotate, then re-insert.

Clean the wall and inside of the wall plate. There may be a uselessly decayed/hardened foam gasket falling off the plate. Just remove this and form a fresh gasket of putty in its place. Getting those long screws to thread into the faucet body can take a while, and they may not reach unless you push the plate (and shower wall) in.

 

Thanks alot for the help man, I got it done today.