I looked at an episode from Season 4, to see if they changed the car, and they did update with a 1984 gold Diplomat (1984 brought black windshield wiper arms).
http://www.imcdb.org/vehicle_964902-Dodge-Diplomat-1984.html

Googling it, I came across this one, which is the same model in the same color:
http://webpages.charter.net/gksutt/diplomat/1985_dodge_diplomat.htm

Hope that helps you.