I have a moen shower faucet where the water mixture keeps getting hotter with very little cold coming through. the temp must be set nearly all the way to cold to prevent scalding.

This is going to be a water heater issue. Not the head.

should have a gearlike part under handle that can be adjusted so as to allow the handle to rotate to more hotter (left) or warmer

do you have hot water elsewhere? if not, might be that your water heater is not heating.
if you do have hot water elsewhere, did you let the faucet run for a minute or 2.
did you have hot water before? is this a new house? new valve?
need a little more detail.
on posi temp valves, if there were no water coming out of the hot side of the valve, the valve will not operate.

Temperature regulating faucet, aka anti-scald, are fast becomring a requirement under local building codes making it, technically speaking, a building code violation to alter the faucets function (assuming someone reported it the loccal buildings dept. That said the function of the anti-scald faucet cannot be altered. You should contact whomever installed the faucet to come back and adjust it so the temperature is more suited to your needs.

these valves can be adjusted by removing the handle and adjusting the white gear that regulates the hot and cold that come out, try going more to one way if it gets colder then go the other way.

IS THIS A SHOWER ONLY? IF SO ,I WOULD REMOVE THE SHOWER HEAD FIRST THEN TURN YOUR WATER ON.THE HEAD JUST MIGHT NEED TO BE CLEANED AFTER 11 YEARS.

spool valve is clogged remove clean replace

probable that there is mineral deposit's,scale buildup,inside. pull cartridge and look in valve body,turn water on to it and flush valve body real good.possible model #1222-if it's posi temp ,#1225 for reg faucet

You can try to rotate the first plastic ring to the left of center a few teeth, this will let the handle advance alittle more to the hot side.

Is this only happening in your shower? Or through the hole house? Maybe you shower head has a flow restrictor in it. Try removing it!