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On-Vehicle Tests
Tools Required:
Rotunda Digital Volt-Ohmmeter 007-00001
A volt ohmmeter (0- to 20-volt scale), such as Rotunda Digital Volt-Ohmmeter 007-00001 or equivalent, jumper wire and a test lamp (12-volt) are the only tools required to perform on-vehicle tests of the complete charging system. Test meter calibration should be checked once a year and the date of calibration stamped on the meter face. It is recommended that this practice be followed by all technicians to maintain test meters at acceptable accuracy.
Troubleshooting or diagnosis is required before actual service can be made in the electrical system. Even where an obvious condition makes replacement of a unit necessary, find out why the unit failed. When a condition is diagnosed correctly, unnecessary service is prevented, the time the vehicle is out of service will be decreased, and the condition will be properly corrected the first time.
Visual Inspection
Preliminary checks to the charging system should be made regardless of the fault condition. These checks include:
Check battery posts and cable terminals for clean and tight connections. Clean the posts and the cables to ensure good electrical contact.
Check for secure connections at the generator output, regulator and engine ground. Also check the connection at the load distribution point (starter relay).
Check the generator belt to ensure proper tension and no slip between the generator pulley and the belt.
Check the fuses/fuse links to the generator to ensure that they are not burned or damaged. This condition, resulting in an open circuit or high resistance, can cause erratic or intermittent charging system concerns.
Before performing charging system tests on the vehicle, note conditions such as: slow cranking, discharged battery, top of battery wet, generator/battery charge indicator stays on with engine running, generator/battery charge indicator does not illuminate with ignition switch in RUN and engine not running. This information will aid in isolating the part of the system causing the symptom.
Isolating the Concern
Battery, starting system, and lamp system concerns can be caused by poor charging system performance. It is also reasonable to suspect the charging system if an overload condition has occurred in another area of the electrical system.
To avoid guesswork, it is necessary to isolate battery, charging system, and electrical circuits to correctly identify the area where the difficulty lies. Check the battery first before beginning any electrical system diagnosis. The battery must be in proper state of charge and operation before the other areas of the electrical system can perform normally.
Battery Check
Check battery to see if it has the capacity and ability to accept and hold a charge. Refer to «Section 14-01». If battery is OK, the charging system should then be checked to see that it performs its function of keeping the battery charged.
The battery capacity, specific gravity and cell comparison test (non-maintenance free batteries only), will determine the ability of a battery to accept and hold a charge. If the battery does not meet specification, replace it with a new, fully charged battery before further diagnosis of other areas of the electrical system.
If the battery meets required specifications, it should be fully charged before proceeding with the diagnosis of other electrical system components.
Constant Current Drain Test
Tools Required:
Rotunda Dwell-Tach-Volts Ohm Tester 059-00010
NOTE:
A voltmeter is sometimes used for this test but it will react to a very small normal drain caused by "always-on" electronic systems such as starter interlock, anti-theft alarm, illuminated entry, etc., which are so small they cause no concern. The test lamp shows only drains which are large enough to cause a concern.
NOTE:
When the electronic instrument cluster is initially powered-up (after a battery disconnect), the "computer" may be energized for as long as one minute causing a 0.25 amp current draw before returning to the normal 0.010-0.012 amp current draw. Therefore, it is important to allow at least one minute to pass (after ammeter hookup) before observing any current measurements.
Check for current drains on the battery in excess of 50 milliamps with all the electrical accessories off and the vehicle in PARK. This test can be performed one of three ways:
Use a clamp-on current probe to the battery positive or negative cable.
Use an in-line ammeter between the battery positive or negative post and its respective cable.
Use a 12-volt test lamp between the battery positive post and the positive cable. If the lamp illuminates, then there is a drain somewhere in the electrical system.
Typically, a drain of approximately one amp can be attributed to an underhood lamp, glove compartment lamp, or rear deck lid lamp staying on continually. Other component failures or wiring shorts may be located by selectively pulling fuses or disconnecting fuse links to pinpoint the location of the current drain. When the current drain is found, the current will drop below 50 milliamps or the test lamp will go out. If the short is still not located, after checking all the fuses and fuse links, the drain may be due to the generator/regulator. Disconnect the generator output wire from the output stud and the regulator connector. If this eliminates the drain, check the charging system to locate the concern.
Charging System
Tools Required:
Rotunda Starting and Charging Tester (VAT-40) 078-00005
In order to check the charging system, the use of Rotunda Starting and Charging Tester (VAT-40) 078-00005 or equivalent tester is suggested. Connect the tester to the battery positive and negative posts and also connect the current probe to the generator output lead (to measure generator output). (When measuring generator output, the tester can also be connected to the battery positive or negative cable. In this case, all electrical accessories must be turned off and 10-15 amps added to the reading on the tester due to the engine operation). With the engine running at 2000 rpm, adjust the tester load bank to determine the output of the generator. The generator output should be near to, or exceed the generator rating at 27°C (80°F). Checkout the charging system as indicated and service if required.
NOTE:
Refer to the Rotunda VAT-40 test procedure manual for complete directions on checking out the charging system.
Indicator System
Normal Charge Indication
With this IGR system four conditions can cause the charge indicator to come on during vehicle operation:
1. No generator output: damaged generator or regulator.
2. Over-voltage condition: shorted generator rotor or regulator.
3. No connection at generator output terminal (B+).
4. No connection at battery voltage sensing terminal ('A' terminal).
With ignition switch in the OFF position, charge indicator (generator or battery) is off.
With ignition switch in the RUN position (engine not running), charge indicator (generator or battery) is on.
With ignition switch in the RUN position (engine running), charge indicator (generator or battery) is off.
Indicator Testing
1. If charge indicator does not come on, disconnect wiring connector from regulator.
2. Connect a jumper wire from wiring connector 'I' terminal to battery negative (-) post cable clamp.
3. Turn ignition switch to RUN position with engine off. If indicator does not light, check for presence of lamp socket resistor. If resistor is present, check for contact of lamp socket leads to the flexible printed circuit. If good, check indicator for continuity and replace if burned out. If indicator checks good, perform Regulator 'I' Circuit Test.
4. If indicator does light, remove jumper wire and reconnect wiring plug to regulator. Connect voltmeter negative lead to battery negative post cable clamp and contact voltmeter position lead to regulator 'A' terminal. Battery voltage should be indicated. If battery voltage is not indicated, service 'A' circuit wiring.
5. If battery voltage is indicated, clean and tighten ground connections to engine, generator and regulator.
6. Turn ignition to RUN position with engine off. If indicator still does not light, replace regulator.
