DISCOVERY
E L E C T R I C A L T R O U B L E S H O O T I N G M A N U A L
CIRCUIT OPERATION
Condenser Fan Operation (MFI–V8)
The Condenser Fans Motors (M113, M121) on
vehicles equipped with MFI–V8 engines operate
when any of the following conditions occur:
3. Coolant temperature exceeds 100C (212F).
4. The air conditioning system is operating.
5. The Engine Control Module (ECM) (Z132)
determines that fuel temperature exceeds
70C and coolant temperature exceeds 110C
after engine shutdown. When this occurs, the
fans are turned on for approximately 10
minutes after the engine is shut off.
Operation with High Coolant Temperature
(MFI–V8)
When the Ignition Switch (X134) is in position II,
battery voltage is applied to the Ignition Load Relay
(K127). The relay is energized, applying battery
voltage to the Condenser Fan Relay (K109) and
the Fan Control Module (Z118). If the coolant
temperature exceeds 100C (212F), the
Condenser Fan Coolant Temperature Switch
(X113) closes and energizes the Condenser Fan
Relay (K109) by applying ground to the relay’s coil.
When the relay is energized, voltage from fuse F3
is applied to the Condenser Fan Motors (M113,
M121) through the relay’s contacts.
Fan Operation with A/C (MFI–V8)
With the Ignition Switch (X134) in position II,
battery voltage is applied to the Ignition Load Relay
(K127). The relay is energized, applying battery
voltage to the Condenser Fan Relay (K109). When
the Front A/C Switch (X225) is turned On and the
Front Fan Speed Switch (X247) is turned to
positions I, II, III, or IV, ground is applied to terminal
86 of the Condenser Fan Relay. The relay
energizes, applying battery voltage from fuse F3 to
the Condenser Fan Motors (M113, M121).
Operation with the Engine Off (MFI–V8)
The Engine Control Module (Z132) monitors fuel
temperature and coolant temperature through
sensors. When the ECM determines than fuel
temperature is above 70C and coolant
temperature exceeds 110C after engine
shutdown, the ECM will command fan operation for
approximately10 minutes. The ECM turns on the
fans by momentarily grounding the Fan Control
Module (Z118) through the BG wire. When the
timer unit is grounded, it starts a solid state timer
and begins to apply ground from its terminal 9 to
the Condenser Fan Relay (K109) through the BP
wire. With the Condenser Fan Relay energized,
voltage from fuse F3 is applied to the Condenser
Fan Motors (M113, M121) through the relay
contacts.
