I will admit I hate my contactors. They're so loud, they hurt my ability to sneak up and run down blind people. (Sorry, that's a bit harsh, but I heard there was a rally at the NY Auto Show protesting against the quietness of EV's and HEV's....)
I'm going to see if I can insulate the go pedal contactor this summer. Click, clack, click, clack. No like.
The resistor is to "pre-charge" the controller, and the diode is to eliminate the back EMF when the contactor turns off... EMF can destroy your controller electronics