Page 183 - CTS - Mechanic Diesel - TP

MECHANIC DIESEL - CITS

TASK 4: Voltage-Drop Tests
Both sides of the circuit should be checked insulated side as well as ground side. Excessive voltage drop caused
by high resistance in either of these circuits will reduce the available charging current. Under heavy electrical
loads, the battery will discharge
An alternator tester or a separate voltmeter can be used. The following steps outline a typical procedure for
performing voltage-drop tests using a voltmeter:

Output Circuit - Insulated Side
1 Check relay continuity.
Connect the ohmmeter positive (+) lead to terminal “4,” the negative (-) lead to terminal “3. Continuity (no
resistance) should be indicated
1 Connect the voltmeter positive lead to the alternator’s output terminal “B” and the voltmeter’s negative lead to
the battery’s positive (+) terminal
2 Start the engine and adjust the speed to approximately 2000 rpm.

3 Read the voltmeter. The voltage drop should be less than 0.2. If it is more, locate and correct the cause of the
high resistance.
Output Circuit - Ground Side

1 Connect the voltmeter’s negative lead to the alternator’s frame and the voltmeter’s positive lead to the battery’s
negative (-) terminal.
2 Start the engine and run at specified speed (about 2000 rpm).

3 Read the voltmeter. The voltage drop should be 0.2 volt or less. If it is more, locate and correct the cause of
high resistance
4 Excessive resistance is most likely causes loose or corroded connections.

TASK 5: Charging Circuit Relay Tests

• The indicator lamp circuit may or may not be control a relay. Depending on the model, when a relay ismay be
a separate lamp relay, the ignition main relay of the engine main relay. Each is checked using an ohm meter
• Charge Lamp Relay

• When used, the charge lamp relay is located on the cowl side of the vehicle. The following steps are check this
relay.
1 Check relay continuity
• Connect the ohmmeter positive (+) lead to terminal “4,” the negative (-) lead to terminal “3. Continuity (no
resistance) should be indicated
• Reverse the polarity of the ohmmeter leads No continuity (infinite resistance) should be indicated.
• Connect the ohm meter leads between terimal’s “1” and “2” No continuity (infinite resistance) should indicated.

• If the relay continuity is not as specified, replacement relay.

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CITS : Automotive - Mechanic Diesel - Exercise 10.1