There is no relay.
There is a interval wiper control, only used in the intermittent position of the wiper switch. Other than that, it's hard wired from the switch, which is why I voted for the comination switch being bad.
The wiper motor itself has a park switch, but if memory serves correctly, if that goes bad, the wipers shut off where ever they were when the switch was shut off. They won't just keep running if the park switch goes bad.
Why worry about the wipers working all the time if it's raining there? When it stops, disconnect the wiper motor.