D 250 Pickup L6-359 5.9L DSL (1992)
Air Intake Heater Relay: Testing and Inspection
RELAY OPERATION
The electronic controller provides a ground path for the air intake heater relays. When the intake manifold temperature is below 16°C (60 °F), the
ignition is in the ON position, the controller grounds the relays, allowing the intake heaters to engage and start the preheat cycle. If the
temperature is above 16° (60°F), the wait to start lamp will not come on and the heaters will not be energized.
CAUTION: Do not energize the air intake heater relays more than once per 15 minutes. If the relays are cycled, the key turned OFF and then
turned back ON, the engine could be damaged. Wait 15 minutes before turning the key back to the ON position.
PROCEDURE
1.
With the engine off, and ambient air temperature below 16°C (60 °F), turn the ignition key to the ON position.
2.
The Wait-To-Start Lamp will come on and the air intake heater relays should click on signaling the start of the preheat cycle.
3.
Check for battery voltage at both air intake heater terminals.
Note: The heaters will only be energized for 10 to 20 seconds, and must not be recycled for at least 15 minutes, so the voltage check must be done
quickly.
