LarryB's 3916301, 3916302, 5265270, 68188370AA Magnetic Relay Switch, 12 Volts
$29.45
AIR INTAKE GRID HEATER RELAY ('03-'07, 5.9L Dodge Cummins)
This Contactor Relay Switch is used on many Cummins engines for grid heaters and starter relays. It can also be used when a 100amp relay is needed. This heavy duty relay will also replace the FORD 7.3L PowerStroke factory GLOWPLUG relay and provide you with years of service over your old factory Ford one. Also fits White Rogers and Sure Power.
Here is a great article on grid heaters and how they work