Truck Repair: 2001 CUMMINS INTAKE MANIFOLD, inner fender, plastic cowl

Question
I CAN'T START MY TRUCK WHEN IT GETS BELOW 30 -- DO THE SOLENOIDS FOR THE INTAKE HEATER HAVE A RELAY SWITCH, IF SO WHERE, -- I GET NO HEAT AT ALL, IT WON'T START.--  I HAVE ASKED WHERE THE RELAY IS,BECAUSE THERE IS ONE,-- BUT NO-ONE WILL TELL ME WHERE IT IS LOCATED, ONLY  "WE WILL NEED TO SEE IT TO KNOW FOR SURE"

Answer
2001 what? ISB,ISC,... Dodge,Frtliner,?? Well Freightliner FL70s are on the plastic cowl near windsheild.Dodge use to be on drivers side inner fender well under the battery.As far as the heater working,there are 2 solenoids because the heater grid has 2 separate grids made into one unit.