I think you are about 10 years overdue for a station upgrade out of that Weather Wizard III.
There is nothing to fix. Literally with no humidity and no pressure sensor. The sensors that you do have...well eh.. Ummm... yeah the whole thing needs to go into a museum. You darn squeezed all that it had out and you got your money's worth out of that station.
Time for a new station bud. A Davis VP2 is going to make a dent in your wallet, but you could also get an Ambient or Ecowitt and end up quite happy for a more modest cost. Let us know if you need more help selecting the right system as there are many options.