Tom,
You probably want a relay with a resistor or preferably a diode built in to limit or eliminate the flyback voltage when the coil is switched. It's the voltage spikes that are pitting the contacts:
http://www.rallylights.com/hella/Hel...%20Relays.aspx
http://www.rallylights.com/detail.aspx?ID=412
David Brady
'02 Blue Bird, Wanderlodge LXi
NC