A sticking windshield wiper switch can cause a delay in wiper operation, especially in cold weather.Google+
Car Problem Reports
Land Rover Discovery Sticking Windshield Wiper Switch May Cause Delay in Wiper operation
Land Rover Discovery Problem
Average Mileage: 114,316 mi (76,000 mi - 160,000 mi)
Visitor, 2003 Land Rover Discovery, 76,000 mi
Works fine in the summer, but in the winter my turn signals and windshield wiper switch don't work until the switch is warmed up.
Visitor, 2001 Land Rover Discovery, 160,000 mi
Wipers wont work until I leave it on full speed for a while guess they need time to warm up
Visitor, 2003 Land Rover Discovery, 85,000 mi
Well it didn't necessarily solve the problem, but in order to get the wipers to work, I turned them to top speed, and hold down the wiper delay. Then it starts to work. Tends to only happen when it's cold outside though.