After a year or so, the single lever kitchen faucet (which I believe is a Delta) we installed, will no longer switch to the cold water side. This just happened yesterday and we are unsure where to start looking for the problem. It is not under the sink, as we have looked at the connections and they are all OK. The faucet itself seems self contained. Do we just take it back or is there a fix?

Replace the ball and the seats and springs. Look for debris when you open the faucet. It takes an allen wrench to remove the handle and the chrome cap nut is thin. Squeeze to hard and it will not turn, use a strap wrench to remove the cap nut. Turn water off first and bleed pressure.