Before you start throwing cash at a new switch, you should not only deoxidize the one you have (my recommendation is
https://www.amazon.com/gp/product/B00006LVEU/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1), but also reference the TM.
TM 9-6115-641-24 has a troubleshooting section. You want to view Table 2-6. UNIT TROUBLESHOOTING "1. ENGINE FAILS TO CRANK." and go through the steps. You may find after the switch is cleaned... its not the switch.
TMs are free... if you don't have a copy, you can download them from the TM section here on the site.