The wipers work sporadically. Sometimes, they only work on high. At that speed they slap back and forth so quickly that during a little drizzle I feel as if the other cars must be staring at me. I can't seem to figure out if it's temperature or humidity that causes the trouble. On several occasions, they didn't work at all.I looked on the Internet and read that it's not terribly uncommon for this situation with Ford trucks. I found one site which showed the step-by-step process to get things to work right. That author thinks that grease gets on the contacts. I've been too lazy to try fixing the situation.