The switches can be removed by first removing the hand grip. You'll see a panel on the back side of this. Use a thin bladed screwdriver and carefully pop this out. From there it should be obvious. I'm not sure you can get into these switches like the older 240 series switches. Certainly clean the contacts on the outside of the switch and reconnect to see it it works. You might just leave the door panel parts off for awhile to verify the fix. If you can gain access to the inside of the switch, then it's your choice, but the driver's switch has the one-touch feature that might complicate a disassembly and fix. To solve the problem promptly, buy a new switch and replace. You can then have the old as a spare.
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John Shatzer, '97 V90 @ 105K