how to test alternator
- Thread starter 1929tudor
- Start date
MikeK
Well-known member
To get the best picture of performance and health, an oscilloscope is needed to see the evenness of the diode performance during a load test over varying speed. The best equipment will give you a graphed printout.
Likewise with a generator, an oscilloscope will "see" the armature while running like a static segment growler bench test would. An open or shorted segment will show up, even though the genny is still working sufficiently to not be noticed with an ammeter and a voltmeter.
Likewise with a generator, an oscilloscope will "see" the armature while running like a static segment growler bench test would. An open or shorted segment will show up, even though the genny is still working sufficiently to not be noticed with an ammeter and a voltmeter.
Mike V. Florida
Well-known member
Simple Alternator Test:
1) Start Car and run at a normal idle.
2) Connect a Voltmeter Directly Across the battery Terminals.
3) Turn on Headlights to High Beam.
4) check the battery Voltage.
*** The Battery voltage Should read between about 13.8 to 14.2 volts. (Possibly up to 14.5 Volts.)
5) Increase motor speed to about 1500 RPM. The Alternator should now produce a battery voltage between 14.2 and 14.6 Volts.
*** If it is Lower than 14.2 volts, the Alternator probably has one or more Bad Diodes.
6) Now, Maintain the 1500 RPM and Turn off the Headlights. Run this test for One Full Minute.
"The Battery Voltage should NEVER Exceed about 14.8 Volts".
***If it Does, the Alternators Voltage Regulator is probably Faulty, OVER CHARGING the Battery.
1) Start Car and run at a normal idle.
2) Connect a Voltmeter Directly Across the battery Terminals.
3) Turn on Headlights to High Beam.
4) check the battery Voltage.
*** The Battery voltage Should read between about 13.8 to 14.2 volts. (Possibly up to 14.5 Volts.)
5) Increase motor speed to about 1500 RPM. The Alternator should now produce a battery voltage between 14.2 and 14.6 Volts.
*** If it is Lower than 14.2 volts, the Alternator probably has one or more Bad Diodes.
6) Now, Maintain the 1500 RPM and Turn off the Headlights. Run this test for One Full Minute.
"The Battery Voltage should NEVER Exceed about 14.8 Volts".
***If it Does, the Alternators Voltage Regulator is probably Faulty, OVER CHARGING the Battery.
BRENT in 10-uh-C
Well-known member
The easiest way to initially check to know if it is charging is to stick a a screwdriver to the back of the case on the metal plug where the backside of the armature is when the engine is running. If there is magnatism, then it is charging.
.
.