I have a hot and a cold faucet in my shower. The cold water faucet has to be turned and fully extended to make the water discharge. The discharge is very weak. How do I troubleshoot this problem? What part is failing?

Hey Jim,

I have put up a image of a shower valve with a center diverter. Yours is the same set up only without the diverter.
Shut the water off and open up the cold water stem and washer assemble. Check the washer and replace if necessary. Check the seat for nicks or rough edges band replace that if necessary. Before you reassemble turn the water back on for a minute to flush out the cold water supply. Good luck, Tom