I just moved into a new house and the basement shower works great on hot water but the cold water barely trickles out. I'm weird and generally like a colder shower so this is a problem.
It's a two knob setup - I have no idea what brand with a lower diverter spout.
The bathroom sink in the same room works great on cold or hot.

Should I attempt to back flush it? I've been reading about cartridges, could it be that I just need to replace something?

Thanks

We have a water tank and pressure pump and no neighbors so I'd have to buy a water pump to try to back flush it I think...

If you have a shut off valve between the tank and the house close it.
If you do not have a shut off valve between the tank and the house turn off the breakers to the well.

Open the sink faucet, hot and cold and to drain the system.

Remove the shower faucet cold handle. Remove the bonnet nut. Remove the valve stem. Depending on the shower valve you may need a set of tub and shower wrenches or sockets. Open valve between tank and house or turn on breakers for short period to flush out valve.
The valve stem may be a compression type or a cartridge type. Inspect it. If compression type replace washer. If cartridge type make sure it is not clogged with debris.

Reinstall and turn water or breakers back on.

Thanks for the response. I drained the system and took off the handle and the sleeve and here's where I'm at now. It doesn't look like the ones I'm finding in YouTube video tutorials. Any advice how to remove the stem?

Thanks

Okay it turns out this was a Moen #1248 cartridge, I finally found one that looked like it in a spanish YouTube video. I have no idea what type of faucet because it looks nothing like the one in the #1248 user manual diagrams.
I put the "stem extender" and knob back on with the screw (after removing the brass "cartridge retainer") and pulled directly out. I was afraid I was just going to break something because it's all plastic but finally after I put all my weight against the wall and pulled very hard it flew out along with some pretty gross gunk and some water.
Cycled the compression pump for a few seconds and flushed everything out, the o-rings on the cartridge looked good I just had to clean it out a bit. Reinstalled, there is a notch at the top of the cartridge that needs to line up when you put it back in then I used the brass "cartridge retainer" and a socket to press the cartridge back in. Put the knob back on and now I have great flow!

Hopefully this helps someone :)

Congratulations and thanks for the update. For a faucet to become that clogged up is unusual. Sounds like you need to install some kind of filter on your well system.