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E N G L I S H
To
diagnose
and
alternators, on a typical GM vehicle, you
must first determine if the system has an
integral (internal) regulator, then whether
it is a type A or B alternator.
The Type A alternator has one brush
connected to t he battery (+) and the other
brush grounded through the regulator.
The Type B regulator has one brush tied
to ground and the other connected to the
battery (+) through the regulator. Next
isolate the problem to either the alternator
or regulator. To do this you need to by pass
the regulator (this is called "Full Fielding"),
ground the Type A field terminal, or
connect the Type B field terminal to the
battery (+) side. If the system now charges,
the regulator is faulty.
CAUTION: WHEN PERFORMING THIS
TEST, IDLE THE ENGINE WITH THE LIGHTS
ON SO THE OUTPUT VOLTAGE DOES NOT
GO OVER 15V. CHECKING AN ALTERNATOR
WITH AN INTEGRAL REGULATOR, YOU
MUST KNOW WHICH TYPE YOU ARE
TESTING TO AVOID ANY DAMAGE TO THE
ALTERNATOR OR REGULATOR.
Alternator Output Voltage Test at the
48
adjust
regulators/
ENGINE
BLOCK
RED (+)
BLACK (+)
Battery (+)
This test checks for alternator output
voltage at the battery.
To measure alternator output voltage:
• Set the rotary switch to voltage ( ).
• Turn all vehicle accessories off.
Connect:
• Black lead to the negative (–) battery
post.
• Red lead to the positive (+) battery post.
Start the engine and run it at 2000RPM.
A reading of 13.5- 15.5V is an acceptable
charging rate.
If the voltage is low, check for:
• Defective alternator or regulator.
• Cracked , glazed or loose drive belt.
• Faulty or loose wires or connectors.
Alternator Output (+) Voltage (Loaded)
This test is necessary only if the vehicle
failed the above test.
To measure alternator output voltage:
• Set the rotary switch to voltage ( ).
Connect:
• Black test probe to the negative (–)
battery post.
• Red test probe to the back of the
alternator.
Start the engine and run it at 2000 RPM.
A reading of 13.5-15.5V is an acceptable
charging rate.
A good alternator will maintain at least
13.6V at the rated current output.
Ignition System tests
Since the Meter can measure from tenths of
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