The upper flipper activates by EOS switch on lower flipper. So if your lower flipper does not work, neither does the upper flipper. Maybe the other EOS switch on lower flipper, that controls current to power winding of lower flipper coil is bad, and the flipper does not pull in with only the hold winding, thus not activating the upper flipper. So check that both of the lower flipper EOS switches are OK.
Flipper operating sequence:
- Flipper button pushed, current flows through lower flipper power winding, since the hold winding is shorted by normally closed EOS.
- Lower flipper pulls in, normally closed EOS opens, effectively connecting the hold winding in series with the power winding and lowering current to safe level.
- At the same time, the other, normally open EOS at lower flipper closes, connecting power to upper flipper coil (that has its own EOS to switch to hold mode)