Mustang V8-4.6L DOHC (1996)
Radiator Cooling Fan Control Module: Description and Operation
PURPOSE
The Constant Control Relay Module (CCRM) interfaces with the Powertrain Control Module (PCM) to provide control of the cooling fan and
A/C clutch. The module includes the PCM power relay to provide power to the PCM.
These relays are contained in one housing, resulting in longer service life and reduced wiring requirements for operation.
CONSTRUCTION
The CCRM has one 24-pin connector. Relays contained in the housing are independent of one another.
OPERATION
The relays contained within the CCRM are interdependent and work with each other. The following describes the different relay functions within
the CCRM:
EEC Power Relay
For any other circuit in the CCRM to operate, this circuit must be powered up. This prevents actuators from being turned on without the EEC
system having control over them.
Fuel Pump Relay
The fuel pump relay circuit controls the fuel pump. The PCM provides the ground circuit for the primary side of the relay. The secondary side
supplies Battery Voltage (B+) to the fuel pump itself.
Cooling Fan Motor Relay
The cooling fan motor is controlled during vehicle operation by the constant control relay module (CCRM)(12B581) and powertrain control
module (PCM)(12A650) which energizes the cooling fan motor under the following conditions:
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When the engine temperature is higher than normal the cooling fan motor starts operating at 105°C (221°F) and stops when temperature
drops to 94°C (200°F).
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When vehicle A/C is on and vehicle speed does not provide enough natural airflow, the cooling fan motor starts running at or below 69
km/h (43 mph) and stops at 77 km/h (48 mph).
Low Fan Control Relay
The Low Fan Control (LFC) relay controls the electric cooling fan. The primary control circuit of the LFC relay is normally high (B+). In this
state the low speed cooling fan runs continuously. To turn the fan off, The PCM grounds this circuit, pulling it low (near zero volts). A "fail
safe" is built into the LFC circuit to run the fan anytime the EEC power relay is activated, should the PCM fail open circuit.
High Fan Control Relay
The High Fan Control (HFC) relay circuit operates the high speed electric cooling fan. If the Engine Coolant Temperature (ECT) sensor
relays a high temperature or overheat condition to the PCM, it activates the HFC. In order to turn the high speed cooling fan on, the PCM
grounds the primary circuit of the HFC relay. The secondary circuit applies B+ to the cooling fan motor.
Wide Open Throttle A/C Control Relay
This circuit controls the A/C compressor clutch during normal operation. This circuit also disengages the A/C clutch as commanded by the
PCM during Wide Open Throttle (WOT) conditions. This solid state relay has two control circuits. One is used to engage the A/C clutch upon
demand from the vehicle operator and the A/C cycling pressure switch. The other control is used to disengage the clutch upon command from
the PCM.
Power Ground
This circuit provides the CCRM with a ground source for operating various controls. The circuit uses one pin that goes to the battery negative
terminal.
