Do you perhaps have the switch in the down position? The switch on the end of the stalk is a 3-position switch. The center position is off. Pressing the top position of the switch turns on interval wiping, pressing the bottom turns on continuous wiping. Just a thought...
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1. Pressing the top position of the switch turns on interval wiping
2. Pressing the bottom turns on continuous wiping.
3. The center position is off