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TM 9-2320-312-24-2
Troubleshooting Section
Repair: Temporarily connect a test ECM. Ensure
Cooling Fan
that the "Engine Monitoring" and the "Coolant
The signal for the cooling fan is provided by the
Level Sensor" are programmed to match the old
ECM in order to control the cooling fan. An input
ECM. Check the test ECM by measuring the
from one of the following items may cause the fan
voltage at the breakout T from terminal 26 to
to turn ON:
terminal 5 again. If the problem is resolved with
the test ECM, reconnect the suspect ECM. If the
A/C compressor clutch
problem returns with the suspect ECM, replace
the ECM.
Engine coolant temperature sensor
STOP.
Air inlet temperature sensor
i01857652
Exhaust brake
Cooling Fan Circuit and A/C
PTO on/off switch
Compressor Clutch Circuit -
OEM installed A/C high pressure switch
Test
Manual fan override switch
SMCS Code: 1359-081-ZS; 1408-081; 1802-081-ZS
The output for the cooling fan is intended to connect
System Operation Description:
directly to the circuit for the cooling fan solenoid.
Program the "Fan Control Type" parameter to
Use this procedure under the following situation:
"ON/OFF". The fan will be off when the ECM output
is ON (energized). When the ECM activates the fan,
Use this procedure to determine if the circuit for the
the fan will remain on for a minimum of 30 seconds
A/C compressor clutch is operating correctly. This
except for the following conditions:
circuit can be connected to J1/P1:41 Input #11 or
to J1/P1:62 Input #12.
Engine start-up
Note: Not all vehicle manufacturers, or all trucks
The "A/C Pressure Switch Fan On Time" is
for a manufacturer use the Caterpillar cooling fan
programmed to less than 30 seconds.
circuit. Prior to troubleshooting, determine if the
vehicle is using the ECM cooling fan circuit.
During engine start-up, the ECM will keep the fan
on for two seconds after the engine has reached
Check the following items in order to determine if a
the programmed low idle (700 to 800 rpm). The fan
vehicle is using the ECM cooling fan circuit:
will be on continuously if the electrical circuit to the
cooling fan solenoid has an open circuit or if the
The "Fan Control Type" parameter must be
circuit for the ECM cooling fan relay has an open
programmed to "On/Off" or one of the variable
circuit.
speed options. The Caterpillar factory default is
None.
Cooling Fan ON Conditions
"A/C Fan On Time" is programmed between one
The ECM will turn on the cooling fan under any of
second and 600 seconds.
the following circumstances if engine speed is less
than 2750 rpm:
A wire is present in the ECM vehicle harness
connector J1/P1 (terminal 11) which is Output #5
The engine is not running.
(cooling fan solenoid).
Engine cranking
Perform the special test for the "On/Off Cooling
Fan". Access each menu in the order that follows:
The coolant temperature is greater than 96 C
"Diagnostics", "Diagnostic Tests", and "Special
(205 F).
Test". Activating and then deactivating the circuit
should cause the solenoid to click if the circuit is
Active diagnostic code for the coolant temperature
working properly.
sensor
The following background information is related
The inlet manifold air temperature is greater than
to this procedure:
87 C (189 F).

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