Probably because your wipers are on intermittent.
Ford Motor Company
The windshield wiper switch allows the driver to make the wipers work either continually or intermittently.
It controls the intermittent wipers
The wiper switch on the ParkAvenue could be bad. Or, the intermittent relay for the wipers could be stuck, causing the wipers to run.
There could be a bad or melted electric connection on the wiper switch connector.
it is possible
there is a problem with your bcm or body control module, have it checked
It's a different system then your regular wipers. They can work when the delay is broken.
Change your wiper inserts.
perhaps the wiper switch is broken and needs to be replaced.-- The delay part of the Switch.
Found out that a relay must be in slot # 8 for them to work