How does Dodge decide which parts will be recalled?

What is your question?

Four thousand parts were on back-order for Dodge vehicles last week. Dallas will be getting in 1900 this week. My Lake Charles LA thinks one of those may be shipped to us this week. The wipers only partially work. It also is affecting the turn signals. If this is the wiper assembly, I am wondering why there is not a recall since Chrysler did a wiper assembly recall in 2009. How many vehicles have to have the same problem before a recall takes place?