Turn fawcet to the right and we get a trickle of cold water. To the left and it's full-on hot water. Any ideas?

Thanks in advance!

What's the brand name of your faucet and what fixture is it on? Back to you. Tom

It's a Delta sink faucet - builder-installed roughly four years ago. I should probably tell you that we have a water softener. Oh, and the shower in that bathroom, and all other plumbing in the house, seems fine.

"It's a Delta sink faucet." A kitchen sink faucet or a bathroom lavatory faucet? Regards, Tom

Hi Tom.

It's a bathroom lavatory faucet.

Shut the water off, remove the handle, adjusting ring,(see images) and the cam assembly. Pull out the ball assembly and the seats and springs. Ckeck and clear any crud that that may be down there. Now turn the water back on to flush out the supplies and valve body. You should have a strong stream out of the open valve body. If not click on back. Reassemble and let me know. Tom