Battery: Testing and Inspection
NOTE: Although these tests will not actually test the battery, they will confirm that the generator, regulator and connecting cables are working correctly and that consequently, the battery may be at fault. Alternatively, the tests may indicate that the fault lies in the generator, regulator or wiring and not in the battery.
Using the Vehicle Battery:
Remove the battery cover.
Ensure that all electrical loads are switched OFF and that the engine is cool.
Start the engine and allow to IDLE.
Whilst the engine is idling, disconnect the battery negative terminal and, using a digital multimeter (DMM), measure the voltage between the terminal on the battery negative cable and the battery positive terminal. If the generator is working, the measured voltage should be within the range 13 V to 15 V.
This indicates the system voltage without the battery in circuit. If the generator is inoperative, the engine will stall when the ground lead is disconnected.
Repeat the test, using the ground bolt, as indicated (shown dotted on the illustration). There should be hardly any detectable difference in the voltage reading (due to minimal current flow); if there is a detectable difference, clean the cable terminal and the adjacent area of the body.
When the voltage has been measured, STOP THE ENGINE.
Reconnect the battery or fit a new battery if it was established that the battery was at fault. Service and Repair
If the cooling fans operate during the above test, the large demand of current will overload the generator and cause the engine to stall.
If the battery is in a low state of charge the voltage will rise momentarily when the battery is disconnected. However, the maximum that the voltage can increase to with this new generator is 25 V and then only for a maximum time of 200 mS.
Using a Substitute Battery
A substitute battery may be fitted for the tests. This battery must be a known good example and must have been off-charge for at least twelve hours, with a terminal voltage of approximately 12.8 V.
Ensure that all electrical loads are switched OFF and that the engine is cool. Start the engine and allow to IDLE.
Measure the voltage across the battery terminals. It should have dropped a little due to the large start current and then risen to a value of between 13 V and 15 V.
If the above test (whichever one used) indicates that the generator is not working then the connections on the rear face of the generator should be checked. If there is a faulty connection, then the generator will not perform correctly no matter how fast it is driven.
Checking Generator Connections:
CAUTION: The engine must not be running when multiplugs are connected or disconnected.
Check that the main B+ terminal is clean and tight.
Check that the IG terminal is clean and making good contact; if this connection is faulty, the generator will never function correctly.
Disconnect the multi-plug at the rear of the generator. With the engine not running and with the ignition switched on, use a DMM to check for battery voltage between the centre pin on the multi-plug connector and a good vehicle ground. If the measured voltage is correct, switch off the ignition and reconnect the multi-plug.
Multiplug Connector:
If no voltage or low voltage is indicated, check for continuity of the harness between the multi-plug and Fuse 5 (10 A) in the Engine Compartment Fusebox - Left Hand Side. Repair any damage to the harness if necessary. It should be noted that if Fuse 5 has blown, the starter motor will not operate and the Engine Control Module will not receive an ignition supply. Consequently, the engine will not start, even with a slave battery.
Start the engine and test for correct charge or voltage level; check as described previously. If not charging and the generator is being driven ie. no belt slipping - renew the generator.