COIL AS 7X1678 - Caterpillar

open circuit is a failure of an electrical circuit that results in no flow of electrical current. An open circuit can be caused by a break in a wire. Most often, an open circuit is caused by a poor connection or a failed connection in one of the electrical connectors that is used in a circuit. The following procedure is a way to check for an open or a poor connection in a circuit.TEST FOR AN OPEN CIRCUIT
Identify the connectors and the wire numbers of the suspect circuits. Use the Electrical Schematic of the machine to identify the circuits.
Turn the key start switch and the disconnect switch to the OFF position.
Disconnect the component and the ECM from the wiring harness.
At one of the disconnected harness connections, place a jumper wire from the contact of the suspect wire to frame ground.
At the other connector of the machine harness, use the multimeter probes to measure the resistance from the contact of the suspect wire to frame ground.Expected Result: The resistance is less than 5 ohms. OK - The resistance is less than 5 ohms. The harness circuit is correct.Stop. NOT OK - The resistance is greater than 5000 ohms. There is an open in the machine harness.Repair: Repair the machine harness or replace the machine harness.Stop.When the resistance of a good circuit is measured, less than 5.0 ohms of resistance is expected. In a circuit that has a wire or a connection that is completely open, the flow of electrical current through the circuit is interrupted. An open can be a broken wire or no connection.A circuit that is completely open will have a resistance that is greater than 5000 ohms.A circuit can be partially open. A partially open circuit will allow some amount of current to pass through the circuit. However, not enough current will pass through the circuit in order to allow the circuit to function properly. A partially open circuit can be caused by a wire that is partially broken. It is difficult to diagnose a wire that is partially broken. The resistance may check "OK" in the section of the wire that is intact. Partial breaks in a wire are not common. When a partial break is suspected in a wire, the current through the circuit should be checked under load in order to verify that the correct amount of current is present.A poor connection can have a resistance that is greater than 5.0 ohms, but less than 5000 ohms. A poor connection can be caused by failed connector contacts. Inspect the connector contacts closely. The causes of failed connector contacts follow:
The connector contacts may be corroded due to moisture that has entered the connector body.
A connector pin or a connector socket may not have been seated securely in the connector body.
A wire may be broken at the pin or the socket.When an open is suspected in a circuit, try to isolate the section of the machine harness that has the open. The complete Electrical Schematic