HARNESS AS-SWITCH 3649120 - Caterpillar

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The presence of water in the bowl may be impossible to see with the naked eye. Water may turn dark yellow in the fuel system. This condition would prevent the ability to differentiate the water from the fuel. This is why the water separator filter bowl needs to be drained when the Liquid Level Sensor determines that the water level has reached the threshold limit.Troubleshooting Procedure
Turn the ignition key to the OFF position.
Drain the water separator filter bowl completely.
Turn the ignition key to the ON position. Do not turn on the engine.
Wait 1 minute. The "Water separator has water" warning should disappear.If the "Water separator has water" warning disappears within 1 minute after the bowl is drained, turn the engine back on and let it run for 5 minutes. If the "Water separator has water" warning comes back on, the fuel has water. Replace the fuel and repeat steps 1 to 4 in order to reset the warning light.If the "Water separator has water" warning does not turn off within 1 minute after the bowl is drained, use the following procedure in order to troubleshoot the system.
Check the connections of the connectors between the Liquid Level Sensor and the Liquid Level Probe. Check the connections of the connectors between the Liquid Level Sensor Gp and the machine harness.
If a bad connection is found, reconnect the connectors properly or replace the pins/sockets as required.
Check that the machine harness connector is sending a power voltage between 8 and 32 VDC to pin 1 of the 4 pin Deutsch DT connector for the Sensor Group.
If there is not a voltage between 8 and 32 VDC on pin 1, the machine harness is defective. Repair the machine harness.
Check that the connector for the machine harness is providing a good return (ground) connection to pin 2 of the 4 pin Deutsch DT connector for the Sensor Group.
If pin 2 is not ground, the machine harness is defective. Repair the machine harness.
Disconnect the Liquid Level Sensor from the Liquid Level Probe. Remove the Liquid Level Probe from the water separator filter bowl. Measure the resistance between the two pins of the Liquid Level Probe using an ohmmeter. The resistance should be between 247.3 kOhms and 262.7 kOhms.
If the resistance is not between 247.3 kOhms and 262.7 kOhms, replace the Liquid Level Probe.
Disconnect the sensor group from the machine harness. At the machine harness connector, short pin 3 to pin 2 for 1 minute and then short pin 4 to pin 2 (ground) for 1 minute.
If the "Water separator has water" warning does not turn off while either one of the pins is shorted to ground, the machine harness has failed and has an open circuit. Repair the machine harness.
If the "Water separator has water" warning disappears, the sensor has failed. Replace the Liquid Level Sensor.