Alternator, Check
The check consists of a performance check and a regulated voltage check, carry out the performance check first.
For simultaneous evaluation of electronic components, use appropriate oscilloscope curve.
The check can be carried out in assembled condition as well as on the test stand. The check here described is for vehicles in assembled condition, which can be applied analogously to the test stand.
A charged battery is required for this check.
| .D. ICON11.tif | 0,75 | 0,75 | tiff;; Important! |
Note the following safety measures:
1. Negative terminal of battery, alternator and regulator must match.
2. Never allow the alternator to run on an uncontrolled open circuit.
3. Never short the terminals to alternator and regulator.
4. Do not reverse polarity of alternator.
5. If an auxiliary battery is connected (e.g. as a starting aid), ensure that the same battery terminals are connected.
6. When charging the battery, note polarity of the charge unit connecting terminals. When the battery is charged while installed, the ground cable must be disconnected.
| .D. ICON06.tif | 0,75 | 0,75 | tiff;; Inspect |
Alternator power.
Circuit diagram:
1 Load resistor, set parallel to battery
2 Battery
3 Voltmeter
4 Ammeter
5 Ignition lock
6 Charge telltale
7 Alternator
| Illustration shows a typical alternator. | |||
|---|---|---|---|
| .P. C6226.tif | 9 | 7,5 | tiff;; |
Disconnect battery.
Close off connecting cable from alternator output terminal (B+ in illustration).
Set ammeter (measuring range 100 A) in disconnected line.
Connect controllable load resistor to battery terminal.
Set resistor in front of connection to 0; connect first to battery, then to resistor.
Connect tachometer.
Connect oscilloscope according to manufacturer's instructions.
Connect battery.
| Start engine and read off resulting current at various engine speeds. | |||
|---|---|---|---|
| .D. ICON06.tif | 0,75 | 0,75 | tiff;; Inspect |
Alternator power.
Adjust load resistor, if the required load currents are not attained.
Shape of the voltage curves on oscilloscope curve - shape should be regular.
Test value: 5 to 7 A.
| If the required minimum current intensity is not attained, or if the oscilloscope picture shows variations, the alternator should be overhauled. | |||
|---|---|---|---|
| .P. C6227.tif | 9 | 7,5 | tiff;; |
| .D. ICON06.tif | 0,75 | 0,75 | tiff;; Inspect |
Regulated voltage.
Circuit diagram:
1 Battery
2 Ignition lock
3 Charge telltale
4 Resistor, for attainment of load current with the battery set in series
5 Voltmeter
6 Ammeter
7 Alternator
| Illustration shows a typical alternator. | |||
|---|---|---|---|
| .P. C6228.tif | 9 | 7,5 | tiff;; |
| .D. ICON06.tif | 0,75 | 0,75 | tiff;; Inspect |
Regulated voltage.
Connect tachometer, volt ammeter and load resistor according to manufacturer's instructions.
Disconnect battery.
Disconnect cable from alternator output terminal.
Set ammeter (measuring range 100 A) between disconnected cable and alternator output terminal.
Set resistor in series to battery.
Start engine.
Adjust load resistor, until ammeter shows the prescribed value.
Read off regulated voltage - ensure satisfactory.
| .D. ICON11.tif | 0,75 | 0,75 | tiff;; Important! |
Only check alternator with parallel switching, charged battery, switch off load resistor and battery after alternator standstill.
Disconnection of load without parallel switching battery leads to voltage transients, which can lead to damage to the alternator diodes.