99 crown Vic windshield wiper only works on high.

99 crown Vic windshield wipers only works on high. What could cause this?

Sounds like wiper pulse board.

Thank you. What and where is that, please? Can it be repaired/replaced?

I'm not sure of what year the pulse board is part of the wiper motor. Try the guys/gals over at crownvic.net

99 crown Vic windshield wipers only works on high. What could cause this?
It could be a multifunction switch or possibly the wiper unit if you try this check scrapyard price. Check what they sell the most.
Best bet is go to alldata and get a years subscription. Use the wiring diagram and check out.