From searching it appears I'm not the only one who launched their wiper switch spring across the garage and then couldn't figure out how it went back in. Found one in the junkyard today and the pic below is how it goes. Photo is oriented with the switch right side up as it would be in the car.
The trick is you need to cross the spring onto both sides of the second contact from the bottom. Note that if you remove the arm and spring you need three hands with super strong pencil-thin fingers to get it all back together properly. Ask me how I know.
Anyway, my single wipe functionality works now, so that's good.
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Tom
'79 TR7
'87 Alfa 75
'91 Alfa Spider