Could we check out some info in your email?
• Are you certain of the model number? Wurlitzer built several variants of the 4300, namely 4300, 4300D and 4300R.
"There is no change at all when operating the various foot selections for the upper manual"
• Do you mean that when, for example you turn on the Upper 16' Tibia and hold down a key, no note plays?
. . . Jan