RAM 2500 Truck 4WD L6-359 5.9L DSL Turbo VIN D FI (1998)
Fuel Heater Relay: Description and Operation
Fig 5 Fuel Heater Relay
Voltage to operate the fuel heater is supplied from the ignition switch through the fuel heater relay. The powertrain control module (PCM) is not used to
control this relay.
CIRCUIT OPERATION
When the ignition switch is in the START or RUN position, it connects circuit A1 from fuse 3 in the Power Distribution Center (PDC) to circuit
A21. Circuit A21 powers circuit F18 through fuse 9 in the fuse block. Circuit F18 supplies battery voltage to the coil side of the fuel heater relay.
Circuit Z12 provides ground for the coil side of the relay.
Circuit A12 from the (PDC) supplies battery voltage to the contact side of the fuel heater relay When voltage is present on circuit F18, the relay
energizes and its contacts close to connect circuits A12 and A93.
Circuit A93 supplies power to the fuel heater. Circuit Z12 provides ground for the fuel heater.
