E N G L I S H
75
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.
3. Alternator Field Current Test
Corroded or worn brushes (or terminals) limit the
alternator’s field current to cause a low alternator
output current. To check the field current, load the
alternator to the rated output current with a battery
load tester and measure the field current by using a
DC clamp-on current probe or use the 10A input jack
on the Meter.
To measure alternator field current:
- Set the rotary switch to DC Amps (A).
- Turn all vehicle accessories off.
Insert:
- Black lead into COM jack
- Red lead into A jack.
Connect:
- Black test probe to the positive (+) battery post.
- Red test probe to the positive (+) alternator cable.
Start the engine and run it at 2000 RPM. The current
reading should range from 3A to 7A.
NOTE: A lower battery voltage will produce a higher
current.
4. Alternator Diodes Test
The best way to perform the alternator diode test is
by removing the diode pack from the alternator, then
touch one test probe to one side of the alternator
diode pack and touch the other test probe to the
other side of the alternator diode pack.
Record the reading and then reverse the test probes
and repeat the test.
On one of the diode tests the Meter should display
the voltage drop across any two diodes in series
typically about 0.8V testing in the other direction
should display “
” which means the Meter has
overranged. If the reading is about 0.4V, one diode is
shorted. A reading below 0.2V indicates two shorted
diodes.
NOTE: Shorted diodes in the alternator can cause a low
current output and run the battery dead overnight.
To measure voltage drop of the alternator diode pack:
-Set the rotary switch to diode test
.
-Disconnect the battery cable from the alternator
output terminal.
- Dismantle the alternator and remove the diode pack
from the alternator.
Insert:
Summary of Contents for UD88
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