Wynns Warranty has shown its customer service address detail for its customers that are shown below. Address detail : 1505 S. DuPont Ave., Unit #I Ontario, CA 91761. customer service number : 1 (800) 255-8138. Below, we are showing a complaint box, where you can post your experiences, complaints, queries, feedback or any type of problem related to the products and services of the Wynns Warranty.