D 250 Pickup L6-359 5.9L DSL (1992)
Air Intake Heater Relay: Description and Operation
Air Intake Heater Relays
PURPOSE
These relays are controlled by the electronic controller. Their purpose is to ENERGIZE the air intake heaters so that they can warm the incoming
air as it enters the intake manifold. The air intake heaters can be ENERGIZED before and/or after engine cranking, depending upon the intake
manifold air temperature. The electronic controller receives a signal from the charge air temperature sensor that indicates the air intake
temperature. If the air intake temperature is at or below 59°F (15°C) the electronic controller will start the air intake preheat or post-heat cycle.
PRE-HEAT CYCLE
The air intake preheat cycle will start if the following conditions exist:
^
The ignition switch in in the ON position.
^
The electronic controller has not received a crank signal.
^
The air intake temperature is at or below 59°F (15°C).
If the preheat cycle is started, the electronic controller will illuminate the Wait-To-Start lamp. Once the preheat cycle has finished, the
Wait-To-Start lamp will go out, and the engine can be started.
If the electronic controller receives an engine crank signal while the preheat cycle is running, the air intake relays will be DE-ENERGIZED
causing the preheat cycle to be aborted.
POST-HEAT CYCLE
The air intake post-heat cycle will begin if the following conditions exist:
^
The engine has been started and is running.
^
The air intake temperature is at or below 59°F (15°C) when the ignition switch was turned ON.
The intake air heaters have two different modes of operation depending upon the intake manifold air temperature, either both heaters are
ENERGIZED or they are cycled ON and OFF individually (while one is ENERGIZED the other is not and vice versa). The amount of time that
the air intake heaters remain ENERGIZED depends upon the intake manifold air temperature.
