CM2150 Electronic Control System – 019-330   Fan Clutch Switch Circuit

Resistance Check

TOC

 CAUTION 

The leads must fit tightly in the connector without expanding the pins in the connector otherwise the connector will be damaged.

If INSITE™ electronic service tool is available, monitor the switch for proper operation. If
not, follow the following procedure.

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Disconnect the OEM harness connector from the ECM connector. Set the multimeter to measure resistance.

Insert a test lead into the manual fan clutch switch input pin of the OEM harness connector, and attach the alligator clip to a multimeter probe.

Insert the other lead attached to the multimeter probe to the switch return (-) pin of the OEM harness connector.

Set the manual fan clutch switch to the OFF position and measure the resistance.

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The multimeter
must show a value of 10 ohms or less (closed circuit).

If the specification is
not correct, there is an open circuit in the return (-) wire or input wire, provided the switch has previously been checked.

If the resistance is within specification, the return (-) wire and switch wire
must still be checked for a short circuit to ground, a short circuit from pin-to-pin, and a short circuit to an external voltage source.

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Check for Short Circuit to Ground

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Disconnect the OEM harness connector from the ECM connector.

Disconnect the manual fan clutch switch from the OEM harness.

Disconnect the clutch switch and the idle validation switch.

Set all cab switches to the OFF or neutral position.

Set the service brake using the trailer brake hand valve. Set the multimeter to measure resistance.

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Insert a test lead into the manual fan clutch switch input pin of the OEM harness connector, and attach the alligator clip to a multimeter probe.

Touch the other multimeter probe to engine block ground and measure the resistance.

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The multimeter
must show a value of 100k ohms or more (open circuit).

If the circuit is
not open, there is a short circuit to ground in the manual fan clutch circuit, provided the switch has been previously checked and is good.

Repair or replace the OEM harness. Refer to the OEM troubleshooting and repair manual.

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Check for Short Circuit from Pin to Pin

TOC

Disconnect the OEM harness connector from the ECM connector.

Disconnect the manual fan clutch switch from the OEM harness.

Disconnect the clutch switch and the idle validation switch.

Set all cab switches to the OFF or neutral position.

Set the service brake using the trailer brake hand valve. Set the multimeter to measure resistance.

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Insert a test lead into the manual fan clutch switch input pin of the OEM harness connector, and attach the alligator clip to a multimeter probe.

Touch the other multimeter probe with attached test lead to all other pins in the connector. Measure the resistance.

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The multimeter
must show a value of 100k ohms or more (open circuit) at all pins.

If any circuit is
not open, there is a short circuit between the input pin and the applicable pin, provided the switch has been checked and is good.

Repair or replace the OEM harness. Refer to the OEM troubleshooting and repair manual.

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Check for Short Circuit to External Voltage Source

TOC

 CAUTION 

The leads must fit tightly in the connector without expanding the pins in the connector otherwise the connector will be damaged.

Disconnect the OEM harness connector from the ECM connector. Set the multimeter to measure VDC. Turn the keyswitch to the ON position.

Insert a test lead into the manual fan clutch switch input pin of the OEM harness connector, and attach the alligator clip to a multimeter probe.

Touch the other multimeter probe to engine block ground and measure the voltage.

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The multimeter
must show a value of 1.5-VDC or less.

If the voltage is more than 1.5-VDC, there is a short circuit to an external voltage source.

Remove the external voltage source.

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Last Modified:  30-May-2008