The fuel heater should have 12 volt power to the connection-- with the key on.
Inside the filter housing, the heater has a thermo switch connected in series to the heater wiring. That switch closes when the temperature in the housing is around freezing. If the temperature is around freezing, the switch should be closed, and the ohms should be about 1.5 ohms. If the temperature is above freezing-- the thermoswitch will be open and the ohm will show open.
You should also make sure the heater ground wire is attached to the primer cup screw.
Chevy 04.5 LLY, 2X, shell, XDR, MikeL Heavy duty up-grade, 6spd, TransGo, deep pan, de-badged, 65 Gallon replacement Aero tank, LBZ-mp, Kennedy pump, shimmed, Pre-fuel filter, tow mirrors, BU cam, gauges, GPS, Sirius, bags, custom grille, fender vents, HD trans cooler- Curt front hitch, footwell lights, load lights, Studs, head gaskets.--- Jerry