Water pressure issue in bathroom

I have a home built in 1963 with two bathrooms, back to back. One bathroom sink trickles hot water, the cold is fine. The other bathroom sink trickles cold water, the hot is fine. The pipes behind the sinks have been replaced at some point and are steel, connected to what I can only imagine as copper pipping. I have no idea where to start. Help please.

Have you done any recent plumbing lately? First thing is to check your sediment screens and look for debris clogging the spout.

(by the way, I moved your question to its own thread, so you will receive more attention)

Thank you. The only plumbing I have done is replacing what is already there. I think I should open up the wall and perhaps take a picture of what is going on.

Before you start demo'ing the wall, start with a few pics so we can understand better. It will also give the experts here a base point to help you troubleshoot your problem. What type of valve do you have in the showers? Many times the scold proof valves go wonky and will cause similar problems. Also, if someone connected two dissimilar metals to your plumbing, you may have a dielectric issue. For this reason, please...pics before demo!

I worked on a faucet this weekend that was getting clogged by the washer from the shut off valve. The washer on the packing was breaking down and clogging the ports on the cartridge. It is never just a simple reason as to why something is happening.

Thank you. I will do that. I will be replacing the vanity in one of the bathrooms as I go. Having to replace 1/2 sheet of dry wall is no big deal if it comes to that.

Deborah, it could be in your faucet body. If it is a lav faucet then turn off the cold side on the faucet that doesn't have pressure and take the supply line off the valve. Take a separate supply line and hook one end on the valve and put the other end in a bucket and turn on the valve all the way. If you have pressure coming out of the supply line then it is the faucet and if not then either the valve is plugged or the pipe leading to it. Its probably not the screen because if that was the case you would have no water pressure from the hot or cold.