Bosch Dishwasher Spray Arm Problem SHY66C05UC /14

[joedadog]

I have a 14 year old Bosch dishwasher that is not cleaning well anymore. I noticed part of the soap is still left in the dispenser sometimes after the load is complete. I looked into the issue and noticed that the spray arms are not both working. Sometimes only the lower arm spins and other times the upper arm spins. I have opened the door several times during a cycle and noticed that only one arm is working. It will go 3 or 4 washes with only the top arm and the last load I did only the bottom arm. I manually move the one that is not spinning through out the cycle to help clean better. I understand there is a valve that controls the switching between the upper and lower spay arms. Is that worth replacing or should I get a new dishwasher.  Thanks for your help.